Recently I did a game in which the coach and player were father and son. I knew this before the game and have had the team a few times before.
During the game there was a play where I called a traveling violation on A1 (the son). A1 doesn't like the call and spikes the ball. Obvious T.
Coach of Team A (the father) pulls A1 out of the game and scolds him. The next time I am in front of the Team A bench the coach comments to me about his son's play, "How could he be so stupid?"
My response: "I'm guessing genetics."
Of course, this was said with a big, exaggerated smile so that the coach knew that I was joking and didn't think I was trying to insult him.