What Causes Severe Depression Along With Asociality In A Person?

Hello, I think my brother has depression. He doesn t want to come out of his room, and when he does he s always pacing around. His room is really small, and the curtains are always closed. He doesn t want to do anything that he used to do. He doesn t leave the house. Apparently he has these instant thoughts that make him feel really bad about himself. They ll be things like killing someone, or something going horribly wrong. They ll go as quickly as they come, but he ll keep thinking about it. He doesn t want to talk about things. He refuses to do anything. When we ask him to do something he ll just say I don t know or maybe later and it s really frustrating. This has been happening for a very long time. We ve tried to be patient and help him but we haven t achieved anything because he simply doesn t want to try. I m not sure of what to do. I ve tried to talk him into doing things that he used to do, like going back to martial arts(which he used to be very passionate about, he went everyday) and going on walks(he was never keen on it, but I ve heard it boosts moods) and obviously just doing normal everyday sort of things like watching movies or playing video games but he never wants to do anything. As I said, he always just says maybe later or I don t know . It drives my whole family crazy when he says this. I put some lavender in his room today(because it s meant to be good for depression or something). I don t know, I m getting really desperate. My whole family is pretty isolated. My parents don t have very good friends. My sister doesn t go out very much with her friends and I m not very close with mine. My brother is basically cut off from all his school friends. He had a period where he took a lot of one-off jobs so he wasn t making any new friends or getting to know anyone properly at all. So, really, he just has us. Our whole family isn t good at talking either. Last year, when we were all dealing with the death of a family relative, we all sort of stopped talking to each other. I had school and exams so I was forced to continue with life. That was when my brother started getting depressed. He didn t really have school or anything, so he didn t have to do anything and he didn t have anything to distract himself. I have a counseler now, but my brother doesn t want help at all which is why it s such a big problem. Anyway, thank you for your time. Christina