Strider babies should be born by mounting one of parents

Striders can spawn mounting each other at times, implying baby striders are carried by parents before they grow up
when you breed striders, one of parents should have resulting baby mounting it
maybe even making it that striders who got someone mounted on them cant be bred alongside regular cooldown, you could still force baby of striders back by leashing it
if striders could breed while having other strider on top of them, then one which has not thing mounted would get baby on, and if both would have some rider, strider or player, only then baby would be left to walk on its own
alternatively baby striders could try to mount adult ones, at least ones without saddles, to prevent baby striders accupying your strider mount while exploring, potentially forcing you to kill those