Thanks for all the replies. Yes they are helpful and insightful.

Yes I have thought about how childhood experiences with my brother may be responsible for the way I feel right now. I will share a few things regarding that:

1) I always felt some jealousy towards my younger brother, even when I was little. For example, I didn't want him hanging out with my friends because I saw them as "my" friends, not his. I suppose this could have something to do with me losing the "baby" status to him at age 2. But I can't say for sure since I can't remember those years. However, I will say that in the years I do remember, I simply do not recall getting ignored or him getting more attention. If anything, I got more attention, being the first born. And yes, I definitely recall being the one with more expectations places on me and he likely did have more freedom to experiment. Not to mention, he was better prepared for everything, since he had an older brother who already went through that phase.

2) During our teen years, my brother really had it in for me. He went through this phase where he would claim that I am favored over him on the family. He would throw tantrums and maliciously attack me over this, often pointing out how I was a loser and had no friends and how he had a better personality than me. And then when he would face a backlash for this he would use it to feed his narrative where he is the victim.

3) We have a younger brother who is 19. He has had girlfriends and actually has one now. However, he does not have the charismatic personality that my middle brother has, and he actually seems to be insecure and emotionally unstable. Like me, he comes across like he is behaving in a way he thinks people want him to behave as opposed to being natural, like our middle brother.

4) I was bullied and ostracized throughout my school years all the way up to high school. Then in high school I was bullied a lot by my brother. My youngest brother was bullied a lot by my middle brother. He would just constantly criticize him and shame him for things all the time. My middle brother was socially accepted at school and did not have to deal with a bully at home like my youngest brother did(which was him).

5) Right now, my middle brother has long outgrown his malicious, narcissistic phase and is generally a pleasant person who seems to genuinely care about us. But of course, this doesn't erase the effects of his past actions, and this may be part of why I feel jealous of him. Also, I sometimes find myself wondering if the reason he harbors no malice towards us now is because he has come to see himself as superior and no longer feels threatened by us. His maliciois actions in the past always seemed jealousy-driven.

6) My middle brother could easily get a girlfriend if he wanted. He has had girls ask him out in the past, but he wasn't interested in them.

7) I think I could get a girlfriend if I wanted to also. I have had girls interested in me over the years and I am pretty sure I have one now. I just don't feel ready for a committed relationship, which is what she is probably looking for.