Graves dissapearing when I move towns

I'm doing a legacy challenge, and I move towns for every new generation. Everything was going fine until it was time for my original sims to die. I have both of their gravestones in one of my sims inventory before the move, but when I get to the new town, only one grave is left in their inventory and the other has disappeared. I really want to be able to have the graves of all of my sims by the end of this legacy, so if someone could help me out with this I would really appreciate it.