My parents may already know (kind of). I'm not going to ask them about it though.
In my family, we don't talk about sex. At all. My brother and I might mention to them that we have a girlfriend, and that's as much as we do. My brother and I don't even talk about sex stuff. I don't know about him, but it makes me very uncomfortable. The funny thing is, I don't have any problems talking about sex with anybody sex. Just my family. Just my close family, in fact. I could talk about sex with my cousins without any problem.
Anyways, a couple of years ago, I was getting ready to go to an anime convention, and I was making a cape that said "Hentai Man" (my perverted alter ego). My mom saw the cape, read it out loud, and didn't say anything. A normal person would ask, "What is 'hentai'?" Right? She didn't say anything, so I assume that either she already knew what it was (somehow) or she was planning to ask my brother what it was when I wasn't around (and he probably would tell her, too). She could have just not given a damn, but she's usually inquisitive, especially when it comes to anime, which has been my predominant hobby for many years.
I figure what I'll do is, I'll take it slow. The "Hentai Man" cape and shirts that say "I Love Hentai" and "Tentacle Sex" are the starter. Then posters of hot anime girls, skimpily dressed and all that. Then figurines of hot anime girls, maybe showing panties. Continue down that road, until eventually I can have porn on my bookshelf with my other DVDs, and they don't say anything or seem concerned at all. After all, I am an adult.
Of course, if I was really an "adult," I could skip the steps and just say that as a warm-blooded guy, I like porn, even if it is animated. Still, it's my fucking parents. That'd be awkward.