Well, I don't know if he is gay or not. He just seems to "act" a bit weird,hear me out. So, me and mum were talking about he "acts". Apparently he's NEVER dated (according to mum) and he's soon to turn 25. Hes never seemed that interested in women. Once he was going to ask this girl out but never did. If mum makes jokes about gays (not homophobic most of the time) he goes a bit quiet and just overall seems to not like it. I'll set an example of the jokes; Me - "dammit it's bent." Mum- "Just like you then!" or if it's like closet jokes. Stuff like that. The jokes don't faze me even though i'm a lesbian. I'm out to mum and I should imagine based on how open I am he knows. So I have no idea. What does everyone else think? Personally I think he is but still in denial.
It's possible, or maybe dating just ain't his jam. What's his social life like? If he keeps himself to himself then it could be he's just not interested, if he's more outgoing then it may be an indicator. I too went through a short phase of feeling uncomfortable at gay jokes, but it wasn't long until I was back to me.
I think maybe you're overanalysing, just seeming uncomfortable at gay jokes and not dating doesn't necessarily mean he's gay. some people are introverted. he'll blossom soon enough.