I agree Kinsao that at our age dating someone that much older than us isn't a big deal, but dating someone 13 years older than you when you are like 15 is different than dating someone 13 years older when you are in your 20's. It is also illegal in the US to have a sexual relationship with someone under the age of 16 in most states, if the person you are with is 18+ (some states it's older) I am sure in other countries it doesnt matter haha.
I can see why someone like Aoi would try to keep it hidden that he is married, because with a job like his, a lot of it has to do with girls going all googoogaga over him. Personally, I would rather people know I was married. If I was married to a famous musician I would like him to state that he is taken at least! They don't need to know who he is married to, but yeah like I said it isn't hard to believe, but it does seem like a rumor someone would start. I am sure tons of these jrockers have serious girlfriends, usually you know which ones don't because they alway talk about being lonely or wanting to find a girl. Which if I remember correctly in an interview a few years ago with Aoi he was talking about finding a girl or something, so if he got married maybe it's been since then. Who knows! maybe he was lying ha.