Zero two wallpapers (Patreon)

In a February 2018 interview with Masayoshi Tanaka (the character designer) and Atsushi Nishigori they stated that Squad 13 members were 16 and 17 years old. Zero Two is 18 years old.

The interview was in Japanese but there’s a translation somewhere. It is a bit surprising since most people thought they were 14 and 15 since its a common age for anime characters.