I recently read the book 'The Time Traveler's Wife'. There is a part where the main character, Henry, has traveled in time and there are two of him, around 15 years old, in the same place and the same time. Unfortunately there is no detail but the author (a woman) makes it clear that they are having some sort of sex. I'm straight other than a little experimentation when I was a kid but the thought of this really turns me on.
Many times while stroking myself I've looked closely at my rock hard cock and wanted more than anything to lick it and take it into my mouth. I've tried but I can't get any closer than about 4'. When I start to ooze pre-cum I love to take it on my finger and lick it off. If there were two of me I would love to rub my cocks together and then lick myself and stroke the other me's cock until it came all over me!