He cheated on his girlfriend, a girl I consider a sister to me, and I had to be the one to tell her.

Happened last month while home for Christmas. I got home earlier then expected, around 5pm, and we ended up going out to help him, who I'll refer to as B, with some last minute Christmas shopping while his girlfriend, who I'll refer to as A, would be getting in around 10 that evening. Some slight background on them: I've been best friends with the both of them since high school, before they became a thing. A and I went off to the same college while B stayed home for the first two years at community college to get his AA before going off to another school. In that time I was rather instrumental in getting him to finally admit his feelings for her and get them started on their up and downs of handling a long distance relationship while in college. In helping her handle things emotionally with that and having already been long standing friends A and I got really close and practically consider ourselves brother and sister.

So back to break. During our time out shopping I'd not seen B in person for 2 months so I did the usual line of questioning: How are thing? How were finals? Whatcha been up to in your free time?. Through all this I learned that his semester was not as hard as A has been telling me it had been for him, that he wasn't caught up studying all night barely able to talk to her but had been out partying, and that he had met someone. The last point he brought up in very hush tone and so I asked further and he tells me that he had slept with this girl 3 weeks prior. I'm this guys friend so I hear him out on it and a whole mess of other things come out able nearly having a threesome, hitting on girls through tinder, and just wanting to whore around next semester. He tells me though that he will talk to A and I press him to confirm that he will since tonight will be the first time they have seen one another since this has happened and even though I'm raging inside that he is saying all this, it should come from him in telling A.

Fast forward to that night, we spend it at the beach where I'd gotten them both Christmas presents which included some vodka for A and Fireball for B. They were rather warm after being in my car all day so I ran off to get some cold mixers from a convince store and they spent the next hour drinking while I only sipped since I'd be driving. By the end of the night B had turned into a major dick, he had not drunk nearly enough to get him even slightly tipsy so it was not having to do with that but A had gone through half the bottle and was a little drunk which was probably more so the issue. I end up taking care of her while he sat or walked off to the side through a lot of the night being just grumpy or ignoring her. It hits 3am and I start to drive them home, dropping off B at his place first then pulling into A's driveway around 3:15. We get to talking some more and she feels terrible about ruining the night and thinks she screwed up something, just rather much feeling like it was her fault B was being grumpy.

This is where things then take a turn. She starts to ask how the day had been with B and wants to know if he said anything about her. Now she had not been oblivious to B acting off the past month and we had talked in depth about what might have been going on with him. She'd even had a list of three girls that B had been spending time with and that she thought something might be going on with. I know from B earlier in the evening know that one of the girls she had suspected something was going on with was indeed the girl he had slept with and that her suspicions where right all along, suspicions that I had been putting down because B was my friend and there was no way, I thought, that he could do that. So, as we sit in her driveway, her pushing to know what had been going on, I don't budge, this is for him to tell her, its not for me to tell. Then she lays this on me. That when I'd run off to get drinks for 5-10 minutes, he'd had sex with her. That instead of telling her that he'd cheated or holding off till there was more time for such a talk that he fucked her first.

So, I told her. I told her what he'd done, things that he had told me he wanted to do, and things he was planning on doing. She toke the initial blow with a firm "I fucking knew it" composure. I ended up driving her over to his house at was was just past 3:30am at this point so she wouldn't end up doing it herself in that state. I sat off in a park a few blocks over till 5am while they talked. She forgave him. Reasons why were given, he admitted that he'd slept with the girl and that he talked to girls on tinder but that the near threesome and wanting to whore around where "tests". That he told me the rest of it to see if I'd tell A, to see if I'd break his trust and tell her those things, and I apparently failed and he didn't want to see me again and that our friendship was done. Apparently I'd not given him the time to tell her himself and explain on his own terms. They talked more the following 2 days home and A ensures me things are as good as they could be. That though it is something that is biting at her inside, and has just broken down repeatedly about, the release of getting him to admit to what was going on and a whole mess of other built up issues that lead to that point has made things better.

I have zero regrets though and I told him so in a text because he'd not talk to me in person. If you cheat, man up to it and talk to your partner. Yeah over the phone sucks and perhaps having the talk in person is best but using the first alone time with them to fuck them is vile. His first thought was not on what she needed to know but what on he wanted physically and thats why I told her. If he couldn't have the trust to tell A the truth why did he deserve my faith that he would ever when that is what was clearly on his mind first and foremost.