Counseling has helped me.
I used to believe that God was watching all the troubles and violence in my family and had a Plan for it all. This slowly caved in over the last few years. But what some might have viewed as strength had its roots in a passivity that slipped quickly into feelings of helplessness and depression.
Broken? Your BIL must get help to realize that his compassion and love make him vulnerable. Who doesn't hurt when the ones you love suffer and die? We all are subject to this breakage, aren't we?
He may have the questions rising from within that many of us have finally spoken out loud about God. And if he is still getting comfort from faith--then I can only say that God didn't answer Job either when he was pressed to the limit. (Ironically the Jews in the Holocaust looked to the book of Job--the man who never got a straight answer from God.)
Is it a comfort to find yourself just a regular unchurched member of suffering humanity? Or is it a greater comfort to believe in God and suffer without understanding God's reason for your suffering? Both are s**t storms.
Strong or not, he should go and TALK--Talk to someone that won't judge him a saint or a sinner for whatever comes out of is mouth.
And glad he could talk to you.
But depression and faith seem to have a real co-dependent relationship with each other-- I found/find it hard to develop a healthy perspective on a life after having thoroughly saturated my thoughts and actions with the ligatures of christian theism for nearly 60 years. All the best to him and to you.