With members of someone else's family I would be honest with the adults in the situation and say I didn't like what was happening, and why. When it comes to your own children I personally find a "let them get on with it" attitude decreases the amount of bickering in the long term. Siblings often fight (in my experience of my own childhood and own children) to get attention to ignoring it works best. But if another baby was hitting mine I would remove my child from the situation and if that was not possible, tell the other parents that you do not accept the behaviour and why.
When Cousin hits, say to her "hitting is not OK" or "hitting hurts DD." Things along those lines - say it firmly, then swiftly move on to a fun distraction for her, like "now, let's see if we can find that pig/rattle/shaker/whatever"
See how that goes. That way they both get the same message, and you're attacking the problem, not MIL/SIL's opinions.
Bookmarks