17-year-old nephew pervert

I’m very confused at the moment. I’m 26 and I have a nerdy 17-year-old nephew pervert named Manuel who’s always talking about my girlfriend Lizzy, saying how round her butt is and asking if I’ve ever had anal sex with her. Manuel’s comments got to me and I warned him to stop. Being his uncle and all, I knew it was wrong of him to pry since my girl would soon be his aunt. Well, Lizzy and I got married last month. We threw a house party and Manuel decided to sleep over. At the end of the party, Lizzy was pretty drunk so I put her to bed and had to send a cousin home. When I got back, the music was still loud in the living room. I went up to the bedroom and my heart stopped. Lizzy had passed out, lying face down, but Manuel had positioned her so that her behind was sticking in the air. He had pulled her pants down and from my view, I could see that he was having anal sex with her and he wasn’t even wearing a condom. I don’t know why I didn’t stop him but watched until he finished. I went downstairs to turn the music off to show that I was home. When I returned to the bedroom, Lizzy was still asleep with her pants pulled back. Manuel came out of the bathroom later and lied to me straight face that he was throwing up from the alcohol. I want to hurt the kid but he’s my nephew. Yet he fucked my wife’s ass. I don’t know what to do.