Most Helpful Guy
This isn't about his age, its about being a family member of your friend. It would be the same awkwardness as dating her brother.
It shouldn't be an issue, although if it goes nuclear (things between you and him end REAL bad), then I can forsee some problems between you and your friend.
Although think this one through -- for now I get it, its mostly about sex and just sex. Got it. But let's say it becomes something more, and then a few years goes by and dating takes off... and heh, it goes so well you guys end up married. Your best friend is now your sister-in-law (of sorts). Maybe too close, right?
Most Helpful Girl
That's fucking hot lol. That's like some shit you'd see in a porno