Mental health and fear: listener question

I am finding myself at a lockdown all thought believed but unable to see a way through this.  My husband died in 2015 when i was 51 and 3 months later my brother committed suicide. At the time of his death he was under mental health care.  I believed 100% that he wouldnt kill himself, and tried to constantly tell my parents that he wouldnt and that it was all attention seeking, but he did.  He hung himself and had a massive heart attack and was not dead when found and taken to hospital and put on life support, after brain scans he was deemed as brain dead and we had to make the decission to turn off his life support.  His actual passing was traumatic for my Mum his son, wife and myself. So much guilt. 

Moving on my son 34yrs  suffers with his mental health and i cannot see that this is ok.  everything in me wants to secure him to secure myself and not have to face this again.  I understand i cannot control anyone or anything but the ongoing fear of this is agonising and not good for our relationship.  What my mind says is well you cant control anything so you know this can happen again, which i know is true and i cant see this any other way and any attempt to feel into it just blocked, nonething.  

If you have time to reply to me i would greatly appreciate it, i just dont know how to approach this.