I know I will be clobbered for this, but he has the body type. Also, his marriage to a woman who is not on his level appearance-wise, and has very masculine mannerisms, is highly suspect (although I also think this latter reflects his control-freak nature too).
I think he knew he had to get married. Remember, “they” didn’t pay for his Harvard Law education for nothing. He was being groomed for the Presidency, and he needed the wife-n-kids on the resume as well.