This may be a strange post. I went back and forth on putting it out there, but I honestly don't know why I feel the way I do, so I figured I'd see if anyone else felt the same way.
I am 23 and I have a twin brother. He's in grad school; I'm working on my second degree (and hoping to 'find' myself and what I want to do). So we're both in the process of "growing up". We both still live at home while we're going to school, mainly to save money. We grew up on a farm somewhat far away from other friends, so I guess we used to be close because we really only had each other to hang out with.
Anyway, we're different people so we've always had our differences. Yet, even though we didn't do everything together I always considered him to be somewhat my friend as well as my brother. I used to be able to convince him to go hiking or kayaking with me, among other things I thought were fun.
But, I guess I digress. In high school he started dating more and did things that were really hurtful to me. He stopped caring what I thought. The most disappointing was when we had our graduation parties; we had them separately on different weekends with groups of our friends. I went early to his and helped set it up, stayed throughout (even as my friends left), and stayed to help clean up. When I had mine, he was with his girlfriend, who was younger, hopping around to other parties. He finally showed up after everyone else had left, and signed my picture with some really stupid saying, and then left again. My mother was angry; my father just said he was a guy and wanted to be with his girl. But it really hurt.
College was generally fine, but I lived for a few years with my friends so I didn't care much about what he did. Last year he got his first serious college girlfriend. I liked her and she always included me in things, but he thought she was too outgoing and social so they broke up. He's now dating another young woman.
Thing is, I actually like his current girlfriend. She's pretty nice to my dog (which is important to me) and I think we have similar humor styles. It's just that she's not as outgoing. Normally that would be fine, but
all they do is hang out with just each other (and sometimes her friends, but she's from farther away so I don't know how much that happens). I try to be friendly but I'm on the shier side so carrying a one-sided conversation is hard for me. For the 4th of July, they went to watch the town fireworks together and I was with my friends, but our groups ended up being near each other. When I was passing their group - which consisted of my brother, his girlfriend, and a bunch of guys we went to high school with - with my friends, we stopped and said hi. I tried to introduce my friends to her but I guess she didn't see us because she just messed with her phone and didn't look up. My brother didn't try to help, either, so we just moved on. Later I asked if he could pick me up afterward and he refused (no idea why, he was going home too) so I ended up calling my parents and had them drive me home.
I never wanted to be a third wheel, but I guess when I pictured my brother dating I imagined being at least somewhat friends with his girlfriend. I didn't imagine going on all their dates or anything, but I also didn't think I'd be so totally written out. When they do little things like run to the gas station nearby for ice cream, if I ask to tag along it's as if I asked to tag along on an intimate, romantic date.
Is this weird? Are my feelings valid at all? Both of my parents have somewhat strained relationships with their siblings, and I always thought that at least we'd have the kind of relationship where we'd respect the other and remain friendly, but it feels like I'm losing that which makes me feel really sad.
I guess, though, FWIW, my brother tends to think he's very intelligent and right in all situations (life just tends to come easily to him) and it's fair to say he doesn't always respect my thoughts or opinions in general, girlfriend or no girlfriend.
My father says that I should just date myself; I'd love to, but right now in my life I have major self-esteem issues so it's
really hard to put myself out there in that way.
Well, thanks for listening/reading my rant.

If you have any tips/experiences to share, it would be helpful!