What to do about cheating team?

I don't really want to expose my friend, but he is doing something wrong. He goes to school in Southern California. He is relatively successful in vex. His older brother is a coder and a mentor. It was confessed to me that his older brother does all of the coding on his robot. I believe it because he isn't very smart in math, so I don't think he knows how to code at all. Should I tell someone?