I keep thinking how they know who is older or younger since Jill keep assuming Hajime is b...

I keep thinking how they know who is older or younger since Jill keep assuming Hajime is big bro but Mishura is lil sis and just realized their name has number in it. Hajime=1, Jill=2, Mishura=3, Gohma=5, Kuero=9, is this how they gonna naming everyone? Lol