Kai because he´d be an awesome father.
Lucas because he´d be so fun, but I´m not sure as I think it would be like having an extra baby in him. He wouldn´t be strict at all.
Yongguk also feels like he needs extra care.
I´d go for Minho? Because he seriously looks like a man that can take care of himself and little humans and would be more of a partner, rather than an extra child. Kai would be great too ♥. He obviously loves his niece and nephew, but it also feels like he has zero ideas about how to be that stricter figure to actually guide little people on their journey through life. I feel maybe Yongguk would be awesome for more sensitive kids ..........what am I doing here? too many details :D.