Difficulties with connecting to people

I don't know what to say, for so long I've been unable to connect with anyone. It's tiring going out of the house only to have no ability to emotionally connect to someone or straight up having nothing to say. I know both, the old DnD group I was in a couple of years ago I had no connection emotionally with all these people I was surrounded by who were so damn close to me. I could easily hold conversation, relate to interests, all sorts of things and yet emotionally I could never get close and now I've left everyone there behind. Now my problem is worse: I never have anything to talk about. It's always been a problem for me at the dinner table where when the adults talk about adult stuff I can't say anything, or when I talked to my brother no one else had room to talk due to some rule of one conversation. Now he's gone to university and I just leave dinner once I'm done eating. My new DnD group I got pressured into via my dad (I'm 21 and still can't get out of his shadow...) and I have nothing to say to those guys either. No intersecting interests, no shared life experiences, I mean they're guys who smoke and listen to country. There's nothing wrong with that but it's hard to talk to them about anything because there's so many things different between them and I, and I only stick around because DnD is fun. Even with my brother around I can hardly talk to him. It's especially awful when he's with my dad because all they talk about is sports which I have no interest in. He tries to get me to talk but he's near useless with advice, not that it matters since he's two years younger than me.

Welp that's the rant of a 21 year old college graduate and dropout who lives with his dad.