Well! I think he's about 17 actually. I think Karen was his first wizard. Because he 発言しました "You restored my faith in celestial wizards". Plus if he was really old, I dout he would have a crush on Lucy. Because he loves her and it's obvious. I dout if he was like really old that 愛 would exist.
When I check the wikia, they never mentioned his age. So we really do not know, but since he is a celestial spirit, maybe they are ageless または something, because they are spirits. For example in this picture, あなた see Aquarius, Capricorn and Cancer with Layla, Lucy's mother. But if あなた see them now with Lucy, they are still the same. So maybe they are ageless または something. But whatever their age they are really good フレンズ !!! :) I hope あなた like my answer !!!!! :)
