In general, what is the lifespan of a person, not the virus, of someone with AIDS?

My sibling had HIV for about 13-14 yrs. they really don't know when he officially was infected. He has crossed over to AIDS and has had it for the last 2 yrs. now. He is 40, yes, he had drug addiction during those years on and off. He is now in the hospital with an AIDS illness related problem. I'm trying to find out more about it - it has to do with severe diarrhea, severe pain, they thought it was an appendicitis, I am recalling something about Sallonoma Poisioning (not sure of spelling) but he has a fever and they are running more test, he has lost 11 lbs in 3 days. He already only weight 110 lbs. he is 5'4" and now down to 99 lbs. Just worried about him and scared I am going to lose him if not later, then sooner. We just lost our mom 6 months ago. Thanks for any straight answers to let me know.