Take on this situation and the things done/said?

I, Ash (24) am dating Cory (23) and have for 2 years but known him for 3. Cory met a guy named Brian (27) 1.5 years ago and they became best mates. Then, 1 year ago Cory met my sister Tess (25) and they started dating.

At first it was a dream to Cory and Brian because they got to be even closer, but in the last month I notice Brian has been making comments to me and about me that have been insulting that lead to an outburst.. this is a super long story so thank you for reading

3 weekends ago it was Brian’s birthday and he invited Cory to go camping on a beach and my sister Tess asked me if I wanted to come. It was us 4 and like 13 other people, some Cory is also mates with. Neither Cory or I have a 4wd but both Tess and Brian do - Brian’s car was full, I went with Tess and Cory went with another mate of his that was going. Tess and Brian had also asked if they could share our cooler with us which we were happy to. However, the cooler in question was a new (expensive) Yeti cooler so Cory and I agreed with each other that we didn’t want it to be slammed shut or sat on until we feel it out ourselves. While we’re camping I hear Tess and Brian slamming it shut so I nicely and quietly asked Tess not to, to which she was kind of just like “oh yeah whatever okay”. Then over the weekend it kept happening, so again I nicely asked her not to but this time explained why and all she came back with was that it’s not a very good esky if you spend that much money and can’t slam it shut. She said it was a waste of money so I just pointed out the interest she spends on her new 4wd and she turned straight to Brian who was across the campsite and says “Brian, Ash is making fun of my Mazda”.. Brian chuckles and says just as loudly (because he is loud speaking do) “yeah and where’s your car?”. I said safe and sound at your shed 😌 and he just laughed, but not in a joking sense - in a way that fully implied he was attempting to insult me for what I don’t have.

Last weekend it was Cory’s birthday and we went canyoning for it and stayed out at a really nice lodge. After the canyoning experience I sent my sister a Snapchat of all the things that went wrong, like a broken nail and that Blundstones aren’t good walking shoes but completely joking. Later on I was in the spa bath minding my own business when Brian rang Cory to say happy birthday. Any time Cory tried to talk about the experience, for example that the walk out of the canyon was a mission and Brian would come back and say something like “yeah Tess said Ash said Blundstones aren’t good walking shoes and I’m wondering who ever said they were” - It was a bunch of little comments said like that and Cory never got the chance to actually talk about his time away or his birthday.

Cory works night shift, knocking off at 1 AM Saturday morning and so on his way home he stopped off at Brian’s shed where he and 3 others guys were having beers, all of which Brian met through Cory. Cory came home at 3ish and when we woke up he told me he was talking about his birthday weekend when Brian says “did you even have sex?”.. Cory says yes and asks why he even asked that and he goes “well I’ve heard your sex life is pretty dry”.. and a couple days earlier I told Tess how Cory was feeling down and out because I wasn’t initiating sex much and he didn’t want to be the one to initiate all the time because it made him feel like a fiend. And Cory also said that he mentioned it twice and on the second he straight up told him to shut his month because he keeps making comments to attack me. I was quite upset when I heard all this because I don’t enjoy being humiliated especially when I’m not in the room, and so I pretty much spent the next day crying.

On the same day, Cory was having drinks with a close friend of his as he was moving out of his place and this guy is also close mates with Brian so they were all there. I went to sleep at about 11:30pm and a couple hours later when Cory comes home he says “Brian and I aren’t friends anymore”. I knew my sister was there and the most sober so I rang her straight away to ask what happened and basically on their drive back into town.. Cory brought up what went on the night before but Brian just kept defending himself. Apparently it got quite heated and Cory made a point that Tess told me something quite serious about Brian and that I never relayed it back to Cory until Brian made those comments the night before for him to use it against him as a way to make him feel bad about himself, nor do I about any other details (i.e. Brian having cheated on my sister with an older woman early into their relationship). Again it was quite serious so Brian kicked Cory out on the highway and took off before Cory had the chance to move so he ran over his foot. When anyone is angry you just need to separate yourselves but he had just ran over Cory’s foot so my sister made Brian go check on him, but it was still very heated. He told me another mate of Cory’s went and picked him and another mate up from the highway, who was with a girl, Brit. This girl is sort of “one of the boys”, and will be very nice to the boys girlfriends face but as soon as something goes wrong in the relationship she will be there sleeping with him, if not during. She did the same thing to my best friend years ago, the same to another girl recently and I know she slept with Cory years ago when he was 17 and apparently became obsessed. I don’t mind the girl but I’m not attempting to make a friend out of her.

With their friendship very much on the rocks, Tess and I wanted them to sort it and so did Brian and Cory. Cory did message him in the morning and didn’t hear back but Brian and Tess don’t have a shower at their place so they come up every Sunday and I live with my parents. Tess told Brian do not let the parents know about this until things are sorted, so when Cory and I walk into the kitchen where Brian is sitting and my Dad is cooking Cory keeps it light, gave Brian a hug and kept the conversation light waiting for the opportunity to move it outside. But, Brian starts talking about it right then and there. Not only that, he says “so how did Ash take it when she found out you got in the car to go out?” - We both said that I was fine fast asleep oblivious to it all. Then, again he goes “yeah I wondered how Ash was going when she heard you got in the car with Brit”. I’ve been with Cory for years and this girl has been friends with all his friends for much longer.. I’ve been dealing with her and it was just so uncalled for and unnecessary. Cory said he was going outside for a smoke in attempt to move the conversation outside but he sat there and said “yeah I’m not moving”.

I completely appreciate Cory for having my back because he has made these slight sort of comments before but much more playful and it just seems to be getting serious and I whole heartedly think Brian would be the same if tables were turned. I spoke to my sister and she’s just as disappointed as I am. Apparently he thought because Cory kept it light it meant he didn’t want to talk about it and that’s why he gave him nothing