I will go ahead and say that you are a very a handsome man. Beautiful smile... but I agree with a previous poster- if I was your friend, I'd kick your ass. Seriously. Could you imagine how embarrassing this situation could be for him? If he was screwing one of your parents, how pissed would you be? Seriously- think about him having your mom or your dad bent over the dining room table, because it's no different from what you're doing.
There are certain rules when it comes to friends- don't fuck their family or their ex's without establishing how they would feel about it. It's just an understood rule, out of respect. Have you considered the issue that this could cause between your friend and his dad, as well? I can't even believe his dad isn't even taking any shame in this. I'm disappointed in him as well...
Your friend is not me, so he may feel differently...But if I was your friend for 10 years, and you slept with one of my parents- there wouldn't be any angry facebook statuses, or hateful text messages, how I would put on twitter that "Dante' is on his way to jail"- because whether you're at home or at work, I'd be coming for you, and I'd fuck you up. Just sayin'... But you're hot!!! Keep that in mind
Take Care,
Dante'