Help with child depression

My son is young still, 6 going on 16, but already a bit nihilistic. He will constantly tell me nothing matters, that nothing in this world is important because we all die someday, and this fact makes him very upset. He gets more nihilistic when he gets in trouble for bullying his sister, which I also wouldn't mind advice on but that's not why I'm here today.I have a pretty dark mental history. I've never been diagnosed with anything, but both myself and my spouse have fought through serious depression with suicidal thoughts. I was never nihilistic and my suicidal thoughts revolved around whether anyone really liked me. My spouse is transgender however and most of her thoughts revolved around never being able to be herself and constantly having to live a lie. We're pretty open with our kids, and they're both confident in their gender (thank goodness, I wouldn't wish the alternative on anyone, but accept it regardless) and my younger daughter is happy enough.But I want to start giving my son the strength he is going to need to survive when hormones hit and if he gets depression. What kind of things can I tell him are worth living for that when he's depressed can help? When I was a teen-ager I believed in a deity and to be frank, that fear stopped me from killing myself. I am now nontheist and I don't teach my kids about God so they don't have that fear of Hell that I had. Please advise! via /r/Parenting http://ift.tt/2vBGGOF