No my Diapers go there!

I am in that "nesting" stage of the pregnancy so on Saturday I cleaned out my boys room and did some rearranging of clothes and things so their new little sister would have some room. One of the items I took completely out of the room where Ian's diapers. I put them in their own drawer in the bathroom and he seemed fine with that. Last night I go into their room and Ian is throwing the babies diapers I had put in Ian's old diaper drawer, all over the floor with a few of his diapers tucked under his arm. I asked him what he was doing and he said that those diapers don't go there and his did. Robert and I weren't sure if he knew that the other diapers where for his little sister so I asked him, "well who's diapers are you throwing on the floor?" He said, "baby sisters!" with this frumpy look on his face. He proceeded to throw them on the floor and when he was done he put his diapers in the drawer and that was that. Talk about territorial!