Family who "walked on water"

Mark had heard a family rumor that his father, grandfather, and even his great-grandfather all "walked on water" on their 21st birthday. So, on his 21st birthday, he and his good friend Brian headed out to the lake. "If they could do it, so can I!" Mark told Brian. Mark and Brian arrived at the lake and rented a boat. They paddled out to the middle. Mark stepped off of the side boat and just about near drowned. Furious, he had Brian drove him back to his grandparents and asked his grandmother why he hadn't been blessed with the same "gift" as the others in the family. His grandmother took Mark by the hands, looked into his face, and said, "That's because your father, grandfather, and great-grandfather were born in January. You were born in July."