Dear Child One and Child Two:
Please, I want you to stop. Stop bickering. Stop trying to prove how much cooler you are, how much stuff you know, how much stuff the other one doesn't know.
I promise that when you get older these things won't seem as important as they do now.
In the meantime, for the sake of your mother's sanity, please refer to this: if you don't have anything nice to say, don't say anything at all. This is something that will serve you well into adulthood. You might as well get on it now.