dbh,
I am so sorry for your loss. Families are complicated for sure and especially for those of us who grew up in alcoholic homes.
Last month my sister attempted suicide for the umpteenth time she is schizophrenic and this is her way of crying for help. It's so gut wrenching to those of us who love her.....I could go on and on, but I just want you to know many of us do understand how you feel.
Please don't go the blame game or guilt yourself into a depression, or spend time with woulda, coulda, shoulda, it is what it is. You owe you family as good of a person as you can be, yes grieve it's natural but don't blame or shame. My sisters therapist told me years ago that there is truly nothing you can do to either prevent or cause the actions of a person who is in such pain. Oh short of calling for professional help if you know they are going to try suicide, but that said he emphasized to me that no one is that powerful over another's life.
Cut yourself some slack, cherish you family everyday and the best response to a tragedy is to live YOUR life as best as you can and for those who are left behind.
May you find peace.