I think my brother might be suicidal?

My brother is 25 and has been unemployed for 6 months, though he's been drinking every night at home here by himself for years, he's frail and unsocial, distant and a loaner. He has a drinking problem and takes citalopram for depression. He never goes out ever only at night to get drink, very estranged. Anyway, my dad has always been having a go at him because he does nothing and stays up late drinking and it's been getting my dad down for months, my dad went mad at him today saying things like "you're a disgrace" "you should just top (kill) yourself and get it over with" and putting him down which was way over, he's very weak and unusual, doesn't fit in, makes no attempt to be social or connect to others despite help. I don't know what to do, I'd say he could be suicidal.