Why does not knowing my grandparents leave such a hole?

You feel a gap where stories should be. Names you never learned, faces you can't picture clearly, wisdom that died with someone before it reached you. This is real grief, even if no one taught you to call it that. Here is what I would ask you first: are you chasing these stories to fill an emptiness, or because you already love these people without having met them? A search that comes from fear says, 'I am incomplete without this.' A search that comes from love says, 'I want to know you, even now, even late.' Do this with others who share the gap — a sibling, a cousin, a partner, your own children. What one person half-remembers, another can complete. The stories were never lost all at once. They are scattered, waiting to be gathered.