I'm sorry, and I can understand loneliness. I was an only child and I always had to be with someone. I always had a one best friend, and if they weren't home, I'd be in distress. I could play by myself, often building models, going fishing, just doing stuff to keep busy. As a musician, I'd spend hours practicing organ and piano, but I was only happy when I was with someone.
It didn't take me all that long to get married, after college and one disastrous first job. I had a psychiatrist when I was in college, and I think they were looking at Borderline Personality disorder. Anyway, I'm okay now because I have my wife. She's diabetic and does kidney dialysis. I can't imagine living without her, coming home to a lonely, empty house, so I do understand, because that thought of being alone is always on my mine.
I hope your brother makes a speedy recovery. Monitoring blood sugar is very important for a diabetic. Oh how I do know. I wish they had blood checkers and insulin pumps back in the day when my wife was young and when we were first married. I think all the damage was done on her in the first 10 years we were married before personal computers were invented and the technology to monitor blood didn't exist, other than peeing on a stick and color coding.