easywhat am-i

A boy and his father are involved in a traffic accident, and the father dies. The boy is rushed to hospital, suffering from injuries. The Head Surgeon is called to operate, but on seeing the boy, immediately declares: "I cannot operate. This boy is my son." How is this possible?
Common Wrong Answers
“The Head Surgeon is the boy's uncle.”
This answer is incorrect because the riddle specifically states that the Head Surgeon declares 'This boy is my son.' An uncle would not refer to the boy in that way, as he is not the boy's direct parent.
“The Head Surgeon is a family friend.”
This answer is wrong because a family friend would not have the personal connection implied in the statement. The Head Surgeon claims to be the boy's parent, which can only logically be true if the surgeon is his mother.
“The Head Surgeon is the boy's grandfather.”
This guess is incorrect because a grandfather would not typically be referred to as 'my son.' The riddle indicates a direct parent-child relationship, which a grandfather does not have with the boy.