A young boy is taking a ride with his dad when a truck runs them off the road, killing the father and critically injuring the young boy. He's Medivac'd to the nearest hospital as the child is lying on the table ready for operation, the surgeon looks at the boy and says "I cannot operate on him, he's my son.
Consider this : Twins are born (lets say two boys A and B) - biological parents die - ends up in foster care - then each are adopted separately.
Lets say their worlds never collided until that fateful day of the accident.
'A' was with his father in the car and lets say this accident took place at 'X'.
Now 'B' had told his parents that day before leaving home that he had some work around the place of 'X'. So when 'B' father/mother who is a surgeon sees the body of 'A' then naturally he/she could say those lines.
Maybe there are some loopholes in this story but still its possible right.
Also it just so happens that 'A' and 'B' were wearing the same exact dress that day :)