I dont think you can help him and this i say because i lost my brother to suicide in 1997 he hung himself in my garage, my father to suicide in July 2004 after a long bout with bone cancer and my mother to suicide in November 2005, so you see I can understand his pain, and you never will.
I am a 32 year old mother of two beautiful girls, one 12 and the other 4, and had i not had them i dont know where my strength would come from, and i would never want them to have my pain. You have to understand that I too cannot forgive either my brother nor my mother. HOW dare they do this to me and my children and for you to tell him that his father was sick just doesnt cut it, because that is your son and his son and parents are to love their children above all and fight with all their strength and inner will to survive and thrive.
You cannot tell him to let go of the anger because you dont understand his anger. Everytime he looks at his children i am sure he thinks of the things that his father will miss, things that when he did them and accomplished them his father was there, and that kills him. His wife unfortunately is just there, and she doesnt care in his eyes because she isnt where he is in the grief process. I am sure that in her way she so loves him and wishes to help him, and i cant imagine what it must be like to be on the receiving end of so much hatred. And that is what you need to understand is that he hates her, if he is anything like me with my spouse, because his life in my eyes is perfect because he isnt in my stage of pain.
I am lucky because on a good day i know that the man i am with is here because of love, otherwise he would be long gone. You see i met him the first day of kindergarten and fell in love that day. I cant imagine a day without him, however, i hate him to the core, because he has this perfect life because he has never felt the pain that i have. the one thing i have as a constant is work and even that i abuse by working hours upon hours in a day.
You need to quit telling him how to feel, let him tell you how he feels, he will come to terms with what has happened but you as his mother cannot save him from this. As mothers we try to ease our childrens pain and that is natural, but i am telling you to back off with that, his feelings are valid and you have to give him that respect to feel them. you can as a mother help him in the way of being there and to help his wife keep her sanity, give him all the space in the world, but connect with her and the children, try to help them understand that time will heal all but that you cannot determine the time limit it takes. Talk about the good times only with your grandchildren, dont mention the bad, and in confidance tell your daughter in law that it will get better as soon as he realizes that he had zero control over his dads decision.
I would love to be able to talk to someome who feels all of the resentment and anger that i do right now, but maybe he is not ready to share, but i am also a mother and i would love to help you get through this so you can in turn help your grandbabies make it through.
Time heals all wounds just remeber that not everyone is in the same time zone that you are!!!!!!!!!