I have 3 very good friends who we'll call A, B and C. We all got along very well together and decided to live together in a 4 bedroom house. In the months running up to finding somewhere to live and moving in together, person B and C started seeing each other and are now in an open relationship, which upsets person A because they have had an interest in person B for a while. This has lead to person A and C disliking and avoiding each other while living together.
Person A likes to organize occasional short vacations and events (and organized everything to do with the house) but has more recently started making a point of not inviting person C and not consulting them when making communal decisions about the house, which clearly irritates them. Sometimes on a large scale of 10-20 people, but more commonly around 2-5. They recently invited me to come on a trip with person B, but without person C, and I'm unsure if I should come or not. Although person A and B have gone on long and far vacations together before all this happened.
I have heard person B saying that they are only interested in A as a friend. I find talking about it to person B an impossible option, as they are the kind of person who tries to get along with everyone and would rather hide under a blanket than face a problem. I think it's because of this personality that A is still after B. I have also heard person C say they still really like person A as a friend after the 'breakup' and I typically find them the more reasonable of the two, although I am unsure if they still hold this view.
I have before managed to diffuse a lot of conflicts between A and C in the past before they turn into arguments, usually with comedy, but don't know how to solve the problem in the long term. We are not entirely satisfied with the location of our house and may move out at some point. I'm worried that when this happens that we will end up going our separate ways.
There are many more factors and complications which may be relevant but I hope you understand that I'm trying to summarize an exceptionally complex relationship into a 5 minute read without confusing the issue.
I'm concerned that if I go on trips without C then they will think I'm on A's side and if I don't then A will think I'm on C's side. How do I avoid this dilemma and are there any alternative solutions?