That reminds me of a set of twins I had. They were 2 1/2, very smart little ones. The best behaved kids I've had, but they would take a collection of toys and hide them in the couch. Or if they got a hold of a bucket they would carry it around all day. It was so frustrating. I had to remind them all the time that they were my toys and I was sharing them so they need to share them too. And if they fought with another child over a toy I would either take the toy and give it to the other child or I would simply take it away all together.

I think you have to put up with the screaming and crying and just ignore it until they understand that it's coming.. .you just have to be patient.