Walk on water
Joe heard a rumor that his father, grandfather and great-grandfather had all walked on water on their 21st birthdays.
So, on his 21st birthday, Joe and his good friend Brian headed out to the lake. "If they did it, I can too!" he insisted.
When Joe and Brian arrived at the lake, they rented a boat and began paddling. When the got to the middle of the lake, Joe stepped off of the side of the boat... and damn near drowned.
Furious and somewhat shamed, he and Brian headed for home.
When Joe arrived back at the family farm, he asked his grandmother for an explanation. "Grandma, why can I not walk on water like my father, and his father, and his father before him?"
The feeble old grandmother took Joe by the hands, looked into his eyes, and explained, "That's because your father, grandfather, and great-grandfather were born in January... you were born in July, dear."