What I stated above: if they don’t have assigned chores, give them assigned chores and then help them with those chores a little when they are good. Say “Since you’ve been so nice and good to Mommy and Daddy today, Mommy and Daddy have the energy to help you with your chores.” Note that this is NOT punishing them by giving them chores, nor letting them get out of anything: they still have to do their jobs, just with you working along side of them. Plus, at htat age, the whole idea that Daddy’s helping ME is a thrill: you can even let the older one supervise: “OK, you earned two pig points today so daddy is gonna help you for two minutes. What do you want me to do?” Use a stopwatch, and at the end of hte two minutes, stop and let her finish the rest.
This depends on the situation and on your kids, of course, but is it possible to just ask them? Senario:
You walk in on Lil’ George with his hands full of daffodils. “Uhoh” you say “Somebody gets a pig point! Go put a sticker on th board!”
Then, you turn to the Little Rasberry: 'Did you get him to pick those berries?"
And you go from there. Only you know if your kids are the type to lie to get out of trouble: some kids are and some kids aren’t, and I tend to think they come out of the womb one way or the other. That said, if your kids are basically truthful, a system that shows that you trust them even when they are, for the momment, bad, seems like a good thing.
But again, trust your gut. It sounds tome like oyu are especially worried that the little girl enjoys egging her brother on, and if that’s the case, then by all means make her responsible. I would, however, sit hre down and explain that the reason you are doing this is because of this pattern of behavoir and that if you see that she stops doing it, things will change: make it clear to hre that the two aren’t linked together forever.