I'm an older guy I suppose. Although I don't think being 31 is really all that old. This is especially true if we use the adage only as old as you feel. I feel pretty young actually with a new lease on life.
I also know that Sean's point to be true as I am seen as a good 5 - 10 years younger than my age. My oldest son is 9 and often thought to be my brother. People get confused when I bring out my other two so that doesn't help with passing. I am not taken as seriously because of my appearance quite often which is frustrating. On the other hand it can also be a blessing in disguise as I am given more of a leeway when I don't know all of the unwritten rules of male social behaviour.