This has nothing to do with manipulation. It's just somebody being an asshole. From what OP said, this wasn't a situation where his brother gave leader to the random. His brother joined the random, like anybody else, no matter your age, would have. There was no reason not to. And then the random decided to waste all of the kids time by kicking him right at the end so a friend could get rewards. This has nothing to do with the kids age, it could've happened to anybody, and has happened to others.