I definitely considered killing myself as a teenager--at least I wanted to have that option. I wasn't even particularly miserable, it's just that life looked like a lot of work and I wasn't interested enough in anything that life offered to justify the effort. Most of the time I'm an upbeat guy and I never even wore that much black, but I still have days where I think like that (20+ years on).
But here's the thing: I had a family that I loved, and I thought about what my suicide would do to them. I wanted to somehow press a button and give my mother a headache 9 months before I was born, but that's not the same as killing yourself. I resolved to get on with things and wait to die of natural causes. Anyway, what's another 70 years? Life is a tiny sliver of somethingness between two infinities of nothingness, and if it lasts 20 years or 90 years it's basically still just as short.
While I was 'getting on with things' I met a few girls...
Now I'm married (3 years, but together for 13) and just as stupidly in love with my wife as I was in the first week of knowing her. I want to continue to be part of her life as long as I can manage. I see myself potentially getting very old while doing so.
Even so, I'm still prone to dark days. I've told her how I occasionally feel, and reassured her that I would never act on those feelings with or without her in my life. I mostly keep those feelings to myself because nobody likes to be with a whining burden and/or loaded gun.
Something to look out for: I've never been all that interested in having children of my own, so I've never pushed the subject with my wife, even though I totally adore my nieces and nephews. That's tied into my feelings about creating a sentient lifeform and lumbering it with a whole lifetime of work followed by sickness/death without any possible way of asking its permission. There's also a (very tiny) part of me that worries that I would go off the edge someday and wouldn't want a child to grow up without a father. So if you feel strongly about having children then maybe you should talk to him about how he feels about having children someday.