A bit of research turned up young Harry's fate, which--as he was born in Britain in 1897--is precisely what you might fear it to be: he died in the trenches on June 7, 1917.
There's a slim chance the song is wrong, for a Harry E Hoad was married in early 1916, and he might have managed to have been a grand-dad after all, but damn if the whole thing hasn't affected a bunch of us. History is closer than we think.