Firstly, this is one of my first posts on reddit and I'm using mobil browser to write this so I apologize for any structural issues.

My (20 ftm) kinda(?) best friend (20 nb) is currently going through a break up with their partner (20 nb). We'll call my friend B, their partner K, and our mutual friend M.

So back in November me and B were super close friends for about 14 months and we went to a concert together. The night of the concert we ended up sleeping together and starting a kind of relationship/situationship. After that until mid January we slept together and hung out consistently, when we weren't physically together we were on the phone. I personally saw our situation as somewhat serious since we'd say "I love you" a lot and we called each other pet names. We talked about our end goals for what we wanted after the first time we slept together and we both agreed we'd hope for a relationship or something resembling a relationship.

In January of this year B briefly mentioned how they wanted to cut back on how often they came to get me which I understood (I know how expensive gas prices are rn). About 2-3 days later B texted a gc we're in with M wanting to complain about someone they were seeing. A few minutes later B texted me separately mentioning it was about someone they slept with. I was a bit shocked and upset when they brought it up since we had agreed to tell each other if we slept with others while we weren't serious. After a short conversation with them basically saying they slept with their friend K, I ended up ghosting B for the end of January and the first half of February because I fell into a bad depressive episode.

When I finally started talking to B and all of my other friends again B and I had a conversation about what happened with K. Essentially they got high together and slept together and were now dating. I was still a bit upset but I didn't really express how I felt since I could tell they were excited for the prospect of being in a relationship for the first time in 2 years.

For the next 2 months they didn't talk to either me or M in the gc or individually (B even forgot my birthday). M and I started talking separately about B's behavior and how odd it was. I finally really told him what fully happened between me and B and how they ended it. M was shocked and just as (if not more) upset on my behalf. After that we started talking about B's relationship and we originally thought K might've been isolating B from their friends. M tried reaching out to B to ask if they were alright and B just kinda brushed them off.

About a week or so ago B finally started talking in the gc asking if me and M could call. We obviously agreed and the 3 of us were on the phone for 5 hours. The call basically consisted of B asking us for advice on their relationship. Pretty much what happened is B and K agreed to having a poly relationship where they both sleep with other people if they ask permission to. From what M and I understand is K wanted a poly relationship where they had a 3rd partner in the future and B wanted an open relationship (though they continue to call it a poly relationship which isn't what they actually want). The first call was B telling us that K wanted to be fully monogamous with B. B asked M and I for advice on how to handle K shaking up the foundation of their relationship. We told B to talk to K about it since B didn't really ask them any questions when they brought up being monogamous. Of course B didn't listen to us. I should probably the K and B were looking for an apartment to move in together (yes, 2 months into the relationship.)

Now, 3 days ago B called me and M once again to talk about their relationship. At this point M and I are a bit fed up with B only talking to us when they need relationship advice. What B told us was they asked K if they could sleep with their friend. K told them no because they had a "funny feeling in their tummy". M and I both told B originally to ask K why they felt that way. This was when B revealed that their friend they wanted to sleep with was A, their high school ex who they reconnected with in December. That's when we told them that the reason K probably said no was because it was their ex (with whom their longest relationship was with). B then acted like they didn't even think about it like that. We told B they should under no circumstance move in with K anf they exploded on us saying they had no other options. M and I were pretty harsh with our advice to B and they left the call.

Now yesterday B called the gc for the 3rd time about their relationship. What they told us is K wanted their relationship to be fully monogamous. B was pretty upset by this since it was a complete 180° from what they agreed upon. This was right after they spent all day together in B's dorm and they had agreed upon an apartment to move into together. M and I told B they should probably break up with K since they are no longer compatible. B simply said they knew that, they said the situation sucked, and they swore off relationships as a whole. We then discussed how K is inexperienced with relationships as a whole and how they should probably have a long term monogamous relationship before committing to a poly one. We also talked to B about how they wanted an open relationship, not a poly relationship, they brushed us off. After that we sorta went in circles before M and I left the call to talk about the situation one on one.

We agreed the relationship was over between B and K and how it was pretty doomed from the start since they both failed to properly communicate their wants and needs. M and I knew B had issues with communication in their past "relationships" including with our ex friend L. Throughout this past week we've urged B to properly communicate with their partner but they never did since they "don't do well with conflict". Currently, M and I are pretty happy with B and K most likely breaking up since they aren't compatible, and B has said it themselves that they'd never be happy in a monogamous relationship since they would end up cheating and they'd never want to cheat on their partner. I ended up asking for outside advice from a different friend group on how to handle everything that's going on with B and 3/5 of them said I was a jerk for being happy my friend's relationship was ending.

tldr: My friend and their partner are no longer compatible and their relationship is pretty much ending. Me and our mutual friend called it and we're happy they're leaving a stressful relationship.

So reddit, am I the asshole?