If the father dies before his child is born, will it lose all claims?

I had a strange situation yesterday: One of my courtiers had a strong claim on an Irish county. I married him to one of my daughters, so I would sooner or later be able to get someone of my dynasty on their throne (or whatever the count equivalent for that is).

Then, the courtier died without giving me a grandchild. I thought all was lost, but a few months later my still widowed daughter had a child.

It was definitely his son, but it did not inherit his claim on the county. Shouldn't it have? I am pretty sure the same situation usually worked out when the father was still around on childbirth.

The situation in the county did not change in the meantime, so thats not the reason for the claim not being there.

Can somebody explain to me what happened?

Claims are passed on at the time of death. Your grandkid wasn't alive (in-game terms) at his father's death, ergo he doesn't get the claim.

Also, not all strong claims are inheritable (i.e. fabricated), though that likely isn't the case here.