Frankly, I don't really get what the big deal is. I mean, yes, she's younger than he is, but he's NOT kissing a 13-year old, he's kissing his teammate, who's in her twenties. Everyone else sees them as a regular guy and a little girl, but they're really Robotman and Elastigirl - the issue here is that everyone ELSE thinks something twisted is going on, not that something actually IS.