Hi phaset, from what I understand she doesn't speak to him online or on the phone. I've never seen her call or text him (doubt she has his number) and I know he doesn't have a Facebook or anything as such.

From a personal stand point here, I really wouldn't consider his behaviour 'nothing'. I have met him, very fleetingly, twice and he is very abnormal (for lack of a better word). I suppose on the occasions I met him he seemed in a way extremely uncomfortable, lost and perhaps even scared? It wasn't just general social awkwardness or a feel of being more at home being an introvert (I personally am an introvert and much prefer my own company) it felt, well, very different. I don't have much first hand experience with him but I believe my friend when she says her brother appears to struggle with most things in life; enough so to make her concerned.