Sons

David heard a rumor that his father, grandfather and great-grandfather had all walked on water on their 21st birthdays.

So, on his 21st birthday, David and his good friend Brian headed out to the lake.
"If they did it, I can too !! !" he insisted.

When David and Brian arrived at the lake, they rented a boat and began paddling. When they got to the middle of the lake, David stepped off of the side of the boat.... and nearly drowned.
Furious, and somewhat shamed, he and Brian headed for home. When David arrived back at the family farm, he asked his grandmother for an explanation.

"Grandma, why can’t I walk on water like my father, and his father, and his father before him?"
The feeble old grandmother took David by the hands, looked into his eyes, and explained,
"David...... that’s because your father, your grandfather, and your great-grandfather were born in January.... and you? You were born in July, dear."