Everything is. My two children spend most of their day arguing about what belongs to whom, and they are always in dire disagreement over whose is what.
They shout at each other across the kitchen table over breakfast every morning, demanding that each of their fruit bars is uniquely theirs. It's true. They each have one. But they are insistent that each brother must know: see this? This right here? It's not yours.
They also argue about things over which there is only one. Specifically, me.
"No, my mommy!"
You get the idea. And my favorite is when they are each tugging on my leg, or better yet, a pocket of my jeans. They'll need to share. That's all there is to it.
I'll try to be as omnipresent as I can.