Meserimus has kids and grandkids that could work - I've some of his family posted but his family isn't set in stone.

Thaddeus flint could have a little sister

Nel Lestranges daughter is open as well.

Murdock greybacks younger daughter, although she also low key wants to be a werewolf like the boys, subject to change now her step mum to be is a bear animagus.

Elizabeth cardew has a little sister although mchb, rather than uc.