Probably a GF who has a primary of her own. The entire time we were together, I felt like it was on my shoulders to make her happy. She felt comfortable and loving with my fiance from the beginning,and he with her, and it was early on decided that it was mainly my problems with "being close to people" that prevented me from being acting in unison with my fiance as a primary to her. And this (it as decided) was why she was unhappy.
I felt incredibly inadequate, stressed and unhappy. Each time there was sort of an explosion of unhappiness in her, when she would try to break up with us, and my fiance would convince her to stay, that things would be different, I would feel huge amounts of pressure heaped upon me to "be close". At the same instant, I felt such pressure to make her happy and such a lack of trust that she could be happy and that she wanted to be in this relationship, that I couldn't be close. It was decided that it was the lack of development in GF's and my relationship that made her unhappy.
So GF and fiance became closer and closer. And I let them, because I knew he wanted it and I felt like the defective one, and I felt my unhappiness signified that I was the defective one among the three of us. The level of care and affection and emotional intimacy he used to have for me transferred in a big way to her, caring for her, keeping her happy by bits and pieces in this relationship she never really wanted, never really believed would work for her. I guess that he thought I knew I had him and should feel secure in that, and therefore did not require as much care (or possibly deserve it, since I was the one doing something wrong)
I'm beginning to see all these things in retrospect more clearly, and it's starting to make me angry. He was concerned if I would be good to him for the rest of our lives, as he has been grieving. As in, would I be as good to him as GF has been in the several months we have been dating her, the several months during which he has showered an enormous amount of care and affection on her, had a lack of the mundane conflicts that long term relationships bring, and basically aligned himself with her in finding problems with how I performed in this relationship.
I think he has been selfish, honestly.
He is not the only wondering if someone will be good to someone over the course of a marriage.
I'm going to have to find something else to do with my anger other than talk to him about it right now. He is too fragile with the grief.