I'm afraid I don't know much about these conditions so apologies if I say anything that may come off as ignorant or offensive; that is not my intention.

I'm trying to help a friend of mine whose brother seems to be going through a hard time. She and him grew up in quite a neglectful and difficult household, their mother I think has some form of personality disorder and perhaps OCD and their dad is very apathetic; neither one of them are very maternal/paternal, it's sometimes hard to believe they became parents (I could NEVER image either of them hugging my friend or her brother, can't even envision them having an in-depth one-on-one conversation with them).

My friend, who is the younger of the pair, has done really well for herself. She went to Uni, managed to find a good job soon after in the city and is now flat sharing there. She is now very independent and much happier than she ever was living at home. However the same can't be said for her brother.

He is older, going to be 30 this year and still lives with her parents. She only sees him when she goes to visit (which isn't very often mind because she is quite distant with her parents) and even then she may not see him because he'll lock himself in his room and won't come out.

He does have a job, but it is part time, he seems very disinterested in it apparently and does not get on with his co-workers; she says she hasn't ever heard him really talk about the people he works with or his job. He takes most of his meals in his room, almost never leaves unless to fetch something like a cup of tea. He very rarely goes out, and although he used to DJ a bit he doesn't really socialise. He's had a few relationships but all relatively short and my friend says she found most of his gf's to be a few crumbs short of the biscuit if you get my drift (she found a lot of them very destructive).

One of the most disconcerting things my friend says she finds is his general inability to communicate with people even on a basic level; he just seems to grunt at people. On one of her visits home she met up with another mutual friend of ours, they ended up going back to her house briefly to pick something up and her brother was in the kitchen, he was making a cup of tea at the time. My friend had yet to even see her brother on this visit until this point and her brother had never met our mutual friend. His sister introduces them to one another and our mutual friend obviously says a friendly 'Hello! How are you?'. He was grabbing milk from the fridge at the time, he just says a muffled 'Heh' to them both and then walks straight out of the room, with the milk!

Apparently he was not always like this, my friend says he seemed pretty normal up until about 14-15 and then he just started to change completely.

She is obviously concerned about him and worried at how unfazed her parents seem to be about his behaviour. She wants to perhaps attempt to talk to him and encourage him to get help but is unsure what the issue may be, whether he is depressed/anxious or perhaps something more along the lines of struggling with autism. Likewise she would like to get a bit more information so she can approach her parents about it as she feels they may undermine her means to help him by saying it's 'just how he is', and that there's 'nothing wrong'. I think she is just worried he is living an unfulfilled life and something is holding him back that may need addressing.

Does it sound like something akin to autism? Or could there be another reason?
Many thanks!