So i \[M26\] broke up with my gf in September and we have now recently back together. We have the same tight circle of main friend group. We have outside friends but this is the friend group we always hang out with. There's me, my two guy best friends and my now again girlfriend. We have been a very tight friend group for about 3-4 years and i have been dating her for majority of that time. We broke up for reasons of not knowing how to fix and move on from arguments but have amended them and are now back together and doing very well.

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However I just recently found out that they almost hooked up less than a month after I broke up with her. Apparently it was a mutual discussion because at the time my girlfriend was really hurt from the breakup, wanted to feel that feeling again and wanted to do it with a friend so she didn't have a one night stand with a stranger. (This is the type of person she is, i do not see it as a bad thing knowing her and how she is in everyday life.) I was her first sex partner and she was my second. Her thought process is that she wanted to be with someone that she knew and can trust. I see that this is an issue on its own but an issue that i believe i understand and can move on from.

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The situation i cannot understand is how my best friend could even put this into his mind. The hook up didn't happen and i am very grateful for that, however it still stings and hurts. Wouldn't you think he would shoot down the idea of this right away? He was the person that my gf went to to talk about the break up and he was the one there to help you process all of this information. He is a very sexual guy and is into a lot of weird kinky sexual activities. One thing, he has a gf (yes they were together when my ex and him almost hooked up) and he lets his gf have hookups with other guy and even one of her best friends. So he asked his gf if he could now also hookup with his best friend (My ex at the time) and she said yes. I have always been curious if he would jump on the idea if we ever did break up just because of his sexual tendencies and now i see that I was right. I don't know his thought process of this all, I don't really want to talk to him about it, I more want to get pass it and still be friends because I do not want to ruin this friend group.

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TL;DR There is a lot if information packed into this. I am trying to process this all and wanted to get other opinions about this situation. I want to be friends with my best friend still but I don't know how to get passed this. However am i over reacting to this situation? Since it never happened should i just get over it? Or should i confront him? Should i have forgave my gf? This is a tricky situation haha.