This was actually last year after prom, it was an after party a lot of us went to. Everyone was drinking and smoking weed, typical parties. There was this one girl that went to my high school, I'll call her Sam. She wasn't a senior, I think she was like 15/16. Anyways, I noticed that some guy from another school, I'll call him John, was pressuring her into drinking and smoking, she eventually did. It didn't really bother me because she was laughing and giving that "playful" kind of no. After about 20 minutes, she had her head down on the couch pillow, complaining about a headache. John just keeps telling her "You'll get used to it. Don't worry. I'll mix it with soda so it isn't as strong." or something along those lines. He just kept grabbing her ass and pulling her towards him. I just told my friend, "dude this chick shouldn't be here." but I didn't want to be a white knight and tell John to fuck off because I didn't know if she was his girlfriend or if she was okay with it. Some time later, John takes Sam outside and tries to get her in his car. (She was almost passed out drunk btw). I went up to him and asked, "Are you her boyfriend?" He just gave me this weird look and said, "uhh she's my cousin, I'm just going to take her home." This was when I knew it was fucking sketchy. This fucking guy really said the girl he was flirting with and pressuring to get drunk and high was his cousin. I tried to ask Sam who she came with but I don't think she even knew what was going on. I pulled her away and guided her back into the house. As I was doing that, John gets in his car and drives away. I found out Sam came with her other friend who was the sister of one my classmates. I told them that some guy tried to get her in his car and when I confronted him, he said they were related. Which was fucking stupid. I don't know what his intentions were but I'm glad I did something.