So sorry to hear about the loss. I am of the opinion there is no pain worse than watching one of your children suffer. When we lose a parent, especially if it is to old age, we grieve but we recognize it's part of life's cycle. The same is at least conceptually true when we lose a spouse or sibling as we become older. But a son or a daughter - young or old - that hurt is indescribable. I've been close to that twice. I almost lost my only daughter in a tragic automobile accident when she was 16. And I know the pain of watching a son and daughter-in-law grieve over the death of a newborn. It is tragic, and the trauma never really goes away. (There are times I still break out in a cold sweat when I have a flashback to my daughter's accident of 18 years ago.) But by God's mercy, we survive. With a much more sober sense of our mortality, no doubt, but we survive. No one is promised eternity in this life. Leaving this body is unfortunately just as much a part of life as entering it.
I am a firm believer in the precept set forth in Matthew 6:6. I commit to you that I will remember you, your family and your friends. After tragedy - sometimes a long time after tragedy - know that there is peace; there is understanding; and that is reward.
Beshalom (with peace).