"I'm your son!"

A couple evenings ago, we were babysitting for our neighbors kids. During dinner, Casey turned to the little boy and said, "Son, you need to eat if you want to get strong....." or something like that. And Ethan pipes up immediately with - "He's not your son, I'm your son!" Casey was caught a little off guard, but we had a good laugh about it. I guess Casey will have to use names.