Grandpa is recently dead or still alive
Dvloper confirmed grandpa was a war veteran,so for that lets say he at least had to be say 42 or at least under 80,however granny lived around the 1850's,so its likely that grandpa was a lot younger than granny and might even be alive or recently dead,this is further confirmed by how grandpa looks a lot less decayed compared to granny,I mean his skin is still normal while granny is grey,he still got lips while granny's decayed and so on