Hi everyone,

Here's the thing: I get along really well with a co-worker of mine in my research unit, to the point that I felt like I wanted to get to know him when I first saw him and get nervous when I see him. Butterflies and chemistry when we were talking while filling envelopes together for two hours after he offered to help me out with it just after we met. But pretty soon after he mentioned that he has a girlfriend, and they just moved in together. We often have to work together. I manage to avoid him as much as possible and I don't think it shows, but today we sat together to discuss an article we're writing together and he started talking to me about his personal life (because we apparently had to catch the same train home and live pretty close to each other - I made up an excuse to take another), bringing up the topic that he lives with his girlfriend, but then saying things about not being happy in his relationship, and that they've been together since he was 15 but that she doesn't care about what he does at work at all. Also on another occasion, in a group conversation (I was having coffee with another colleague and he had chipped in), he was talking about how it's incredibly difficult to tell the difference between friendship love ("philia") and how to distinguish a long term partner from just a friend.

On both occasions, I would not respond and rather point out how incredibly valuable it must be to know each other so well and the importance of friendship in a relationship, but they make me very uncomfortable and I'm not sure how to respond properly when this occurs. I refuse to be a home wrecker or support him in his complaints as a female co-worker that gets along with him well, so usually try to point out the value of their relationship or try to change the subject when he brings it up.

Also in general I don't like the position I'm in and welcome any advice on how to handle this or make this easier for me.

TLDR: feelings for a coworker who is in a relationship, succeed in hiding this and avoiding him as much as possible, unsure about how to respond correctly to him implicitly expressing doubts/complaining about his gf