Jonathan Carnahan is Evelyn's brother in The Mummy movies. He, of course, becomes Rick O'Connell's brother-in-law when Rick marries his sister after the first The Mummy. Jonathan tends to be the bumbling idiot and the comic relief, but we love him anyway.
Jonathan: Pull me up. Pull me up. [he sees the huge diamond on top of the pyramid] Jonathan: Wait, wait. Let me down. Let me down. Rick: It's not worth your life, you idiot. Jonathan: Yes, it is. Yes, it is.