Have you asked your relative where she/he may have put them when unpacking because you can't find them?

Right now all you have is circumstantial evidence that they are responsible. Who else could it be, right? You would need proof that they took the items. Who made the move for you? Is it possible that they stole you property?

You can make a list of all the missing property and stop by the local sheriff's office and tell your story. They will tell you if you should file a police report.