Question about suicide?

I have only met my future BIL 2 x and both were at family weddings. They live in another state. The brothers are not very close and talk once in a while. At the recent wedding (Mid May) BIL told my fiancee he had attempted suicide 2x. His wife and I had a very short talk about how worried she is about him. His FB posting are getting darker and darker. Started with things like "can't sleep again", "does anyone else have a bad feeling today" I can tell by friends responses I have no friends" "why even go to bed, it will just be as bad as yesterday". I have expressed concern over this to my fiancee but he doesn't seem to want to get involved. Today's post was "when I die bury me in my Nationals t-shirt." I just called my fiancee and told him and his response was "I'll call him later today". Both will just brush it off as the family tends to do with all things. I have had battles with severe depression and an overdose that put me in ICU for 10 days on a respirator. I know how helpless and hopeless and "there is no one who will miss me" feelings all to well. That's what I see going on here and it seriously scares me. My fiancee will have a chit chat conversation and not address the real issue. I worked hard with a psychiatrist and a therapist to turn my life around and can't even imagine that dark place again. My question comes down to this. Would I be out of line to call his wife, tell her a little of my story, listen to her and offer any support I can? I can even offer some suggestions as to what I did to recover. I have been asked many times to tell my story to people.. I talk with survivors groups about not trying to figure out what "they" did to cause this and school groups including parents about signs/symptoms of depression, treatments options, and suicide prevention. Do I call the wife whom I don't really know, what do I share with her or do I leave it to my fiancee?