how can a toy bring out the worst in a kid?

you think i'd be talking about a toy gun or violent video game but i'm not .i'm talking about a simple power wheels 4 wheeler .my two nephews can not seem to share it and go into a tantrum if they are told they can't ride it for any reason .i wish my dad hadn't brought it for them cause i can only see it being more trouble .and of coarse my dad isn't having to deal with it .so when my nephews are suppose to be out in the yard sharing it they do nothing but fight .then one of them ends up crying .and all i get out of it is frustrated .i hate trying to keep the peace .i really do .i wish we could just do like rodney king requested "can't we all just get along?" .its a nice sentiment but i don't think its possible .as long as there is more then one being capable of independent thought peace on earth will never be

but why would two kids like a toy so much they'd risk having it taken away because they can't share it .i told them numerous times that if they didn't share it and share it nicely that neither one of them would get to play with it .and this morning the younger one asked to ride on the four wheeler and i told him it was to early .he then begin to pout and started calling me stupid and the started crying .i really hate that damn four wheeler