I don't have any relatives between 13-15 that I'm aware of. They're mostly little kids or much older than me.
i'm tired of guessing, so you ought to just come out and say which close relative you want to bed.....unless, of course, you've been "brainwashed" into being ashamed of that sort of thing.
edit:i'm not going to debate why adults shouldn't be sleeping with 13 year olds. the fact that you think it should be up for debate is more then a little unsettling though.