Who's Younger?

I woke this morning to Joseph and Sarah arguing about who is younger. I was doing my best to ignore it, but they had to ask my opinion. Sarah said that she was younger. Joseph said that he was smaller (he's 1/2 inch shorter) so he was younger. I explained that since Sarah was born last, she was younger. But apparently that has nothing to do with it--at least in Joseph's mind. They decided to see who weighed more. Joseph weighs a pound more. That settled it. Sarah is younger :)