26.10.2026 UPDATE: Updated to the 1.6 version:

Sims will now have normal teeth on aging up to teens (vampires will have those with vampire fangs) instead of the random ones. I lost my mind because of all those teens with gold or missing teeth

Fixed an issue which caused the 'Something went wrong' notification and EA genetics usage at birth. It's for cases when the algorithm tried to choose a face region preset from only CC presets (which can't be recognized by the game itself properly). Now the game resolves itself what to do with such presets, but other aspects of genetics will be made by this mod

Remove the old files (the settings are fine) and download the newest 1.6 version!

09.10.2026 UPDATE: Added the Spanish, Portuguese Brazilian and French translation links

Finally I made one of the most challenging and wanted projects I planned to release. This mod collection provides completely another genetics system.

The main module adds essential genetics features we so missed in the TS4!

Inheritance from Grandparents

If you didn't know, the game completely ignores the appearance of grandparents. If you ever had an offspring with hair color or presets that reminded a grandparent, it was either a bug or a coincidence.

But this module is another story.

With a predefined chance (by default it's 80% but you can change it) an offspring inherits the parent appearance. It includes a skin tone, voice, face and body presets, sliders values, an occult race (if they have any) and hair and eye color. The remained chance applies on the grandparents appearance (by default 10% per grandparent).

So, this feature makes the offspring genetics way more interesting and diverse.

Smart Sculpts and Sliders Inheritance

The mod forces the game to apply the sliders which are related to the inherited sculpt from the same source (i.e. nose sliders from parent with parent's nose inheritance).

What about CC Sliders?

The mod recognizes hundreds of custom sliders! I took them from this master list (huge thanks to the author!). It means, that the algorithm will check which region of body / face a slider belong to, and will be inherited with other sliders of the same region. If the slider has opposite gender variant, it will be considered too. Otherwise, it will be inherited only if a child has appropriate gender.

Some of the sliders are inherited random such as height ones, because they don't actually belong to lower leg or neck. Yup, I manually checked every slider, and don't forget, that almost every slider package has more than one slider! I spent two days on it

So, please, just check this list if you're not sure whether or not my mod supports this slider. I hope you understand that it will be impossible for me checking every slider constantly.

Other CC sliders still work fine, they just will be inherited randomly.

I won't update the mod just for one more slider, because it takes lots of effort and time. Consider it too, please

And keep in mind, that I don't guarantee that one or another slider works correctly, I'm not their creator. I just add support, that's all.

What about CC Presets?

It's another story, as the game itself doesn't include them into the genetics, as the presets map of age and gender doesn't contain information about CC presets. Though, I'm investigating, can it be solved by manual mapping or not.

Natural Hair and Eye Color

It's so annoying that we don't have any possibility to 'dye' hair or make Sims wear colored contact lenses because the game percepts it as a change of genetics.

This module lets you to assign the natural hair and eye color, so you can freely change the Sim appearance and it won't affect the offspring genetics. Instead, the algorithm looks for flags of natural hair and eye color.

How does it work?

On the game launch the mod looks for player Sims and checks the hair color tags and the eye color values on their appearance and assign corresponding traits.

Regarding hair color, the highest priority have hairstyle and eyebrows. If the mod doesn't find appropriate tags (i.e. your Sim doesn't have hairstyle and eyebrows), it will look for a body hair color. It also works with CC as well until they have proper tags.

But no worries even if the mod didn't find anything appropriate (say, you use non default CC eyes) or you think a Sim has actually another natural color. With testingcheats enabled, Shift + click on the Sim and choose the correct color from the 'Choose Eye Color' or the 'Choose Hair Color' interactions of the Genetics Overhaul category.

Unnatural Hair Colors

Only teens and older may have unnatural hair color, that's why children have, for example, red hairs until they age up and get pink hairs. It works good in the vanilla, but if you have the Unnatural Hair Colors for Little Sims by SnarkyWitch, the mod will apply the unnatural hair color right from the infant age.

Eye Color Cheat Specifics

Because of great amount of eye colors (68 at this moment!), I divided it into categories by occult race. Yup, we now can assign any eye color regardless if a Sim is Human or, say, Vampire, but still it has the most appropriate occult race.

If you play without any occults, just check the first group of colors.

Otherwise, you can find a desired eye color in Vampire, or Mermaid, or Alien category and etc, if you have a corresponding game pack.

Please note that the occult eyes have quite extraordinary official names and I did my best to adapt it so you can understand more easily how do they look. But still, pay attention to the icon first. All of them come from CAS swatches.

Occult Eyes Fix

If you play with occults, you might notice that an offspring often inherits random eye color instead of the parent' ones. That happens because most of the occult eyes don't have a unique tag (just an occult race), so the game assigns random occult color.

But the mod memorizes the eye color ID instead of the tag and applies the corresponding eye color trait when creating an offspring. That's why a child will have exact eye color instead of the random one.

There is a special case for a few occult eye colors: they don't have a child version, they are for teens and older. The game just assigned them a brown color, but I mapped them to have a child similar color. For example, children with Blue Ghost fairy eyes have blue eyes until they age up.

Even if something went wrong and the mod hasn't replaced eye color on aging itself, you can use the 'Force Update Eye Color' cheat. It's available for teens and older who have these specific eye colors.

Occult Mutations

It's turned off by default, but when this feature is active, there is a chance (you can set it up) that a child will inherit a different occult race rather their parents and grandparents have, even if they aren't occults.

Adjusting Settings

Starting from the 1.1 version, you can adjust the settings directly in the game, just Shift + click on a Sim and choose the Genetics Overhaul Settings interaction. You'll see this menu:

The Reset to default option return these settings:

Do not inherit grandparents presets

Chance of Inheritance from Parent: 80%

Occult mutations are turned off

Inherit Grandparents Presets

This feature is turned off by default in case you want more fixed and predictable inherited presets. If you set true instead false, then the grandparents presets will be considered too.

Chance of Inheritance from Parent

The setting indicates possibility to inherit from parent instead of grandparents. This value should be between 0 and 1 inclusive. The grandparent inheritance possibility then (1 - inheritance_from_parent) / 2, or 10% per grandparent by default.

Also, the chance is applied on each genetics attribute separately. So an offspring may have eye color and nose from a grandmother, hair color and voice from a grandfather and other things from a parent.

If a parent doesn't have parents, then, naturally, only the parent genetics will be applied. If they have only one parent, the script will consider the parent genetics with the same chance (80% by default), and the grandparent genetics with 1 - inheritance_from_parent chance (20% by default).

Mutation Chances

Choose the Occult Mutations option and you'll see this menu:

There will be settings only for those occult types which game packs you have for.

All mutations are turned off by default, but you can set a value between 0 and 1 inclusive for any occult race you want. Please note, these chances don't affect possibility to inherit occult race that parents or grandparents have, only inheriting occult races they don't have.

What does the last setting mean? it's a possibility of an offspring becoming a random occult from non occult, considering all chances above. Say, you set a spellcaster mutation chance to 10%. It means that with 10% chance a fairy offspring will become a spellcaster instead. Yet, if the chance of mutation from non occult is 0, there is no chance to become a spellcaster, if it's a non occult offspring.

I haven't included ghosts and aliens, because it seems weird for me. Aliens can only come from Sixam, and ghosts are dead Sims with a soul basically.

It also supports a hybrid system if you have a mod for that. Then each inherited trait can be mutated (i.e. two traits can change instead of one).

Recreate Offspring

Starting from the 1.1 version, a report is generated for each born Sim (including NPCs and pets), you can find them in the reports subfolder:

Do not change anything in the file names or content!

The reports are generated for two reasons. First, you can send it to me if something went wrong when a Sim was born. Second, the data from these reports can be used to recreate an offspring.

What does it mean?

Say, you faced an issue with my mod and a born Sim is somehow buggy. It would be a disappointment to just delete this Sim and start everything over.

Instead, you can use the 'Recreate Offspring' cheat on the mother of this offspring (in general, on a parent which can be impregnated). Shift + click on the parent, and then select another parent. In this dialog you'll see only acquaintances of the same species of the first parent, which can impregnate (if that's a dog or cat. they also must be not neutered).

If these parents have an offspring with the mod report, you can choose the data of this offspring.

Right after that, the parent will be in labor and will give a birth to a new Sim. This one will have the same predefined data as the selected offspring has. But this Sim won't get their own report, because it will be an endless loop of the reports with the identical data. And it's just meaningless, as this Sim is generated by the EA mechanics. The original offspring won't be deleted automatically, so if you want it, do it manually (i.e. using the MCCC cheats).

If the selected Sims don't have children with the reports, you won't be able to choose anyone.

The cheat is available:

on not pregnant humans which can be impregnated or on female pets (if that's a cat or dog, they also must not be neutered) of the active household

this Sim must be on home lot, since they can't give a birth on other lots

the household size must be 7 at most (you need an extra space for a new offspring)

In any case, I advise you to make a save copy right before your Sim giving a birth with my custom genetics algorithm.

Compatibility

The mod is compatible with Wonderful / Wicked Whims (18+) by Turbodriver, Relationship & Pregnancy Overhaul by Lumpinou, Realistic Childbirth by Pandasama, NPC Family Genetics Fix by deadlystringnyc (it just doesn't use my enhanced genetics yet, but we're about to make a version to support my mod), occult hybrid mods. pregnancy interaction mods and so on.

Actually, I haven't found any conflicting mod yet, but feel free to ask me about compatibility with a specific mod.

It's compatible with MCCC by Deaderpool too, you just need to turn off a couple of features, because they don't support grandparents' genetics. Click on the Computer and open the MCCC menu. Then CAS -> Offspring:

Disable Use Parent Physical Attributes and Use Parent Skintones

Other appearance related things work without conflicts.

Also, my mod supports Genetic Unnatural Hair Colours for Little Sims by SnarkyWitch , so your infants will have unnatural hair color too with this mod.

Limitations

First of all, the mod doesn't affect offspring creation in CAS, because the CAS code is unavailable to see and be modify.

The mod mechanics are ignored when Wicked Whims adds a dead offspring to the family. But I don't think it's something important.

When a Sim becomes infant, it has the hard coded hairstyle. I made it to ensure the hair color will be applied correctly. I also don't think it's a big problem, you can change it later.

If you use a non default eye color, it may be skipped by the mod when assigning the eye color trait.

If the CC hairstyle doesn't have proper color tags (happens when a creator makes all swatches based on the black ea swatch), the mod looks for tags on the eyebrows, and after that on body hair. Keep that in mind and don't be surprised if you see black hair color on white haired Sims. Just set the traits manually.

CC presets are ignored, and not only by the mod, but by the game itself, because they don't exist in the special presets map that is used on genetics applying. I advise you to not use custom presets on Sims you want to have children. Or be ready to fix the offspring face in CAS.

The attraction system from Lovestruck ignores the natural eye and hair colors, but I think it makes sense, since Sims should be attracted or repelled by the current appearance, not by the biological one.

The mod works with pets too, but they don't have natural color system, because it's made different.

I can't think of other limitations, but you can ask me anyway.

Check the compatibility status HERE

REQUIRED

Lot51 Core Library

Base Game compatible

CONFLICTS

Read the compatibility section

TRANSLATION

Russian by me

French translation link by Hope

French translation link by ElianasDiaries

Brazilian Portuguese link by Jezzamia

Spanish translation link by JA Simmer

FAQ

No interactions?

You haven't installed Lot51 Core Library correctly

You haven't enabled testingcheats

How to set / reset the settings?

Read the Adjusting Settings section

The settings have been reset?

You inputted incorrect value somewhere, read the adjusting setting section

Regarding other questions, first read the compatibility and limitations sections, and other feature related sections

How to recreate a child if something went wrong?

Read the Recreate Offspring section

No Recreate Offspring cheat?

You haven't installed Lot51 Core Library correctly

You haven't enabled testingcheats

You click on a Sim from not active household, or they can't be impregnated (CAS setting, already pregnant, neutered in case of cats and dogs, not enough free slots in this household)

For more details, read the corresponding section

Does it work with CC sliders?

Yes, read the 'What about CC Sliders?' section

Will I add Slider_Name into support?

I won't update the mod just for one more slider, because it takes lots of effort and time. Consider it, please

What about CC presets?

They are ignored by the game itself, not just by the mod, when genetics is applied

Is there a conflict with <Mod Name>?

Read the Compatibility section, and if I haven't mentioned this mod there, ask me

INSTALLATION

Put it in the Mods folder no deeper than one subfolder

Don't delete the JSON file, it has essential settings! And don't move it anywhere

The newest mod version is 1.6, remove all files and settings and reinstall the mod if you have the older version!

DOWNLOAD

Read about the update and download HERE (Public Access)

This is the most difficult thing I have ever made, so I'll be very grateful if you decide to support me 🙏

OTHER MODULES

All modules from this collection are independent and don't conflict with each other

Better Inheritance

No Weird Age Up and Random Genetics

P.S. I can only help if you provide me with the details of any issues you are experiencing. Read THIS before writing a bug report (via the link below, not in the comments section).

Contact me | Buy me a Coffee | Bug Report | Mod Status Sheet