I'm surprised this didn't already get a mention here. Yesterday, Tony Gwynn Jr collected his first big league hit, a double. 24 years ago to the day, his father collected HIS first hit, also a double.
from ESPN.com's game story:
Tony Gwynn Jr. had a pinch-hit double in the Milwaukee ninth for his first major league hit. His father's first major league hit -- also a double -- came exactly 24 years earlier to the day, on July 19, 1982, for the Padres.
The younger Gwynn received a standing ovation when his accomplishment was announced between innings.
"He hit a double, too," said the rookie outfielder, who was told before the game that it was the anniversary of his dad's first hit.