For two underage characters there’s toy ship if they’re both below their teens.

I suggest teen ship, direct as it is, for when both characters are in their teens.

For a mixed teen/child romance perhaps tag ship (referring to how teenagers sometimes call younger characters “tag alongs” when they’re forced to associate with them.

For noncon ships, I suggest lock ship, as a pun on “the rape of the lock”, and also how one might consider the ship “locked” and must be “forced”.

For dubcon I suggest the partner pun pick ship, both as one might pick a lock instead of forcing it, and also how one might select or “pick” a partner.

We’re going to put together a glossary and some fun games to spread the terms later.