Doody is right Ellie..you can't let your brother hold you hostage to his threats of commiting suicide. He may very well kill himself someday but that isn't your "job" in life to live in fear of it nor think you can prevent it.
You have already had to endure much more in your life than you should have from a sibling and from parents who were irresponsibile.
There's nothing wrong with loving the brother you wish you had...the one who cried..but you have to take of you.
Oh, and this forum loves new people....welcome.