Ben in his youth was a police officer and his son Joe always looked up to him and wanted to be like him.
Ben gave his son Christmas gifts with not-so-hidden messages behind them, such as a watch because of how late he always ran and weights because Ben thought he was too skinny. Ben was told by his son that when he has a son, he'd give him fine presents.
Joe became a cop just like his father. The watch which Ben passed to Joe was later passed down to Joe's foster son, Barry Allen.