My brother is dating someone for the first time, they just got engaged, and whenever I think about it I feel so rejected and abandoned I feel like I'm burning in a fire. We used to hang out so much together and now I feel like he is going to move on from me and it really hurts. I dont even dislike his fiancee. She seems nice.

Thinking about their relationship also awakens my own relationship trauma, in which I was never able to establish a relationship successfully but became intensely attached to multiple people, then realized later that my attachment was not normal as I got passively rejected each time.
 Seeing his success and everyone around him congratulate his relationship makes me feel like a failure, as I've never been able to find someone who cares about me that way, and every time I liked somebody who didnt care about me I would dream about taking them home and my family meeting them and integrating them into my family. I have always dreamed of being able to openly express affection for someone without coming off as clingy and pushing them away, and it always feels like my love is not important, my feelings are not important, and I dont count.

It hurts because it seems like he found love so easily while I feel like I literally need it to stay sane and absolutely no one will give it to me. I am in therapy now and I have been working on trying to feel whole without feeling the need for someone, but all the relationship trauma I've been through floods back when I see his relationship. It hurts so much.