I know who catnaps brother could be

Bro-Mon New Monster Ideas
1

It could be Huggy Wuggy

2

Also I think it should be a legendary

3

Bro, :face_with_raised_eyebrow: Catnap does not have a brother.

4

Uhh now there’s more poppy playtime

5

arent all the little plushies all siblings, idk the lore