I have 8 yr old twin nephews and everything, everything is a competition to them. they are each good at different sports but when they play the same one the other gets their feelings hurt if he's not as good as his brother.
They're not the same age, but my two youngest girls are the worst. The latest thing is trying to yell "I want that!" to lay claim on a toy when it's commercial comes on. I'm like "You know they make more than one of those, right?"