I don't think they go together at all, sorry.
Rosalina and
Olive might go together, because they're both quite unusual and old fashioned sounding. I'd call that an old fashioned chic style.
Also, I suppose
Mckenzie and
Brett go together as they're both pretty modern. I'd call that a trendy/modern style.
However, I don't think all 4 of them sound like a sibset.
Mckenzie and
Rosalina are too different to each other.
p.s. is
Mckenzie a boy or girl?