hi My DS is almost 14 and has been seeing a girl of the same age for a couple of months. He recently found out she had cheated on him, several times.He was going to break it off with her, but then he spoke to her on the phone and she had a handful of excuses such as 'well the first one was a dare, so was the second time, the third time the boy kissed me even though i didn't want him to, and the fourth time I was really drunk 
and didn't know what I was doing.' so he has made up with her.
He also told me that she apparently can't stop drinking,to the point of being 'para' once she has had a sip of cider, she just can't stop. He certainly has not got drunk -yet- luckily they go to different schools and she is regularly grounded for a variety of reasons so their relationship is mostly over the phone/fb.
I do not think banning him from seeing her will achieve much, although I am not happy about him seeing her (especially the fact that she apparently gets paraletic)
Iv'e been trying and failing to point out whats wrong here, but he won't have any of it. How can I get through to him what is and is not acceptable in relationships in general, not just this one.
I know he will learn himself that this 'relationship' is not good for him and will be there to support him but I want to try to teach him about red flags etc, not easy as me and his dad split when he was young (his dad was EA) I had a second relationship a few years ago which ended with me being very badly beaten by the man (i had not learned about red flags) so he has not really had any kind of example of a normal relationship.
if anyone has any ideas or ideas of advice websites aimed at teen boys that would be great.
thanks