Septimia
It's really sad when that happens.
It's been said before - buy birthday cards for your GS, write them and keep them. Say in them how much you love him despite not being able to spend time with him.
Each birthday and Christmas - or more often if you wish - quietly put into a bank account the money you would have spent on a present. Arrange that he can access this when he's adult and his parents have no say. If you can, try to organise it so that this arrangement doesn't antagonise his parents.
You could also put together a book of photos and stories about your side of the family. Put it with the birthday cards so that he knows you remembered him.
With any luck, circumstances will change long before he grows up.
I would add - put those letters and cards into a bank vault and give instructions how to access them when he's an adult.



