In one case, it ended up with older boy consistently bullying smaller sibling. By the time parents started to intervene, it was habit and it took months to be stopped. The younger kids still somewhat dislike brother, altrought he treats her much better now.

Other cases I have seen were roughly similar. Work it out may work out may not. But pretty often it amounts to enabling bullies - and even blaming the victim if the victim does not defend itself in perfect magical non noisy calculated way.