Father and son were going to the airport and they had a car accident and the father died and the son had a lot of severe injuries..he was taken to the hospital and when the surgeon came to operate on him, the surgeon said that "I can't operate on him because he is my son."
you never said the son was the son of the father who died, who could be someone else's father or Father could refer to him being a priest, or the surgeon could have been his mother, how is that even a riddle let alone a tricky one?