John Stamos discovered some disturbing news about his great-grandfather, Vasilis Stamatopoulos, when he traveled to Greece on Who Do You Think You Are? John found out that his great-grandfather had been murdered when John's grandfather was just a baby. Plus, John learned that he and his grandfather share the same name of his great-grandfather's killer.
John went to the village in Greece where his great-grandfather lived and met his dad's cousin, one of many Stamatopoulos family members that still live in that village. She shared the story that was told to her by John's great-grandmother.
Apparently, there were some tensions brewing between the Stamatopoulos family and the Koliopoulos family. In an attempt to smooth things over, Vasilis made Ioannis Koliopoulos the godfather to his child, John's grandfather. Although, it didn't seem to help during a scuffle between Ioannis and another man, when Ioannis ended up shooting Vasilis in the head.
John's Greek cousin showed him where his great-grandfather was murdered, and then took him to the cemetery where he is buried. And after some reflection, John realized what kept his family members going through those tumultuous times. John said, "It all goes back to family. Everybody says, family, family, family. Family gave them the strength, gave them the courage."