Children of either sex should outlive their fathers and their mothers as well.
I sense (but have no way of knowing) that Harry's wife isn't living. I imagine that's some relief to him, that she didn't experience this tragedy. Like you, I hope Harry finds the strength to cope and can give some of his own strength to his son's wife and their children, assuming he was married.
My grandmother was predeceased by everyone in her family -- besides her parents, her sister, her husband, first one daughter at 35 and then her other daughter (my mother) at 45. She (my grandmother) died about 6 months later, most assuredly of a heart broken too many times.