Cadmus was the original owner on the resurrection stone, which was sooner or later handed down in ring kind to Tom's grandfather Marvolo Gaunt and his uncle Morfin Gaunt right before Tom stole it. The later generations on the family, however, did not understand that the ring contained the stone. https://josuekqvzd.wikijournalist.com/3729445/5_simple_statements_about_harry_potter_explained