I've tried explaining that the child will be made fun of by his peers and that later on he'll struggle to find work. They don't listen, my bro and his wife are both body builders who think by naming their son Absolute Unit, he'll hit the gym frequently and be strong. I care a lot about this because I've agreed to watch the kid during the days since both parents work long hours and I work as an author, which I can do from home. How can I be more convincing?