Way back in the days of my youth, I was a 16 yr old barhopper...I was in another town close to where my family is from. It was a magical night at Ronny's Real Honkytonk, I met a guy, who knew some people in my social circle, after dancing a few times on the smoke filled dance floor we left with a cousin of mine and a friend of his. After we had a few drinks on their porch, it led to a hot makeout session. I wasn't into having sex back then, so it just involved some heavy petting and kissing. Never really thought about this guy again, until a couple years ago when I was going thru my mom's closet, found a box of things I probably shouldn't have looked in, but I was nosey and did. There was an envelope with my name on it, inside was a letter that told me all about the situation with my mom and my real father. I never knew his name, although I've known since I was 8 that I had a different dad from my sibling. I saw the name and later it hit me. Gross I've made out with a family member. After a little digging, I found out this guy was my real dad's cousin. So he was whatever that makes us kin.
Ugh! It still grosses me out that I let him put my tongue in my mouth, even if it was unknowingly. I couldn't imagine kissing a cousin willingly let alone fucking one.
My advice is tell him to cut the grabbing, touching, feeling crap out and go fuck a blow up doll or cheap prostitute if he needs an easy lay. If you ever need a conscience check, ask yourself now when I have kids do I really want them to go and fuck my niece or nephew??? Whatever you answer for your kids then apply to yourself.