RB, i hope it's just a stage because we are struggling with the same thing. DD1 is 3.5 and DD2 is 2 and 2 months. They are constantly fighting over things. I think it has a lot to do with their immature brain. Sharing and taking turns is a difficult thing to learn. But i must say, since i put DD1 in kinder, just 3 weeks ago things have improved. she is learning 'play skills' from the other kids and is playing much more productively and nicely with her sister. Fingers crossed that this too shall pass?!