I'm not sure what I should do about this, if anything. DS and DD1 (6 and 3) are fairly reasonable kids on their own, but their behavior together is awful. They put each other up to all kinds of bad behavior and trip all over themselves laughing. They'll rough-house until someone ends up crying. They'll "cuss" or spill food at dinner for laughs. They throw their clothes and shoes everywhere, again for laughs. They don't register that I'm telling them to stop till I physically remove one of them. I'm glad they're enjoying each other's company, but this doesn't seem to be going in a healthy direction. Should I fight this? How? Or just be happy they get along?