My oldest son is 30 years old with some gray hair and is about 6-feet, 2-inches tall (188cm). I'm about 5-feet, 9-inches tall (175cm). People who know me, but have never met my son often think that I'm younger than I am--it's probably because of my silly personality. But when they eventually meet my son and see how old he is, they always look back at me in disbelief that I would have a son that big and that old. While they're trying to decide what to say to me that would be polite, my usual response at that moment is, "Yeah, he's older than me."
So, that's my answer here to the question about my age: I'm younger than my oldest son.