@catoutofbed@octodon.social Hmmmmmm...
So in primatology (and zoology in general, but especially primatology because primates tend to do* this), sometimes the siblings of a parent will take care of the parent's kiddos instead of having their own. They're called "alloparents".
I know this is combining suffixes and prefixes in a way that doesn't actually make sense, but "allobee" sounds really cute.
Pibling is good too. :3