DB webcomic CH6 page 90 (Patreon)

Crescentia:

As a sidenote where the "mommy" part comes from:

Banshee adresses her underlings as her children (my boys, my girls ect.), even though they are not actually related, so some of them call her Mommy in return. Max being one of them who adress her as such :3 

Tl;dr: "Mommy" is a nickname. they are not related.