There have been father and son combinations on the same team in the major leagues before, but never with the son as a pitcher. Brett Bochy made his major league pitching debut with the San Francisco Giants on September 13, when his father Bruce, manager of the Giants, summoned him to the mound in the sixth inning of a blowout 17-0 loss to the Los Angeles Dodgers.

See related story about Bruce and Brett Bochy at the link below from Yahoo Sports:
http://sports.yahoo.com/news/brett-bochy-makes-mlb-history-as-first-pitcher-to-play-for-his-father-064413737.html