The Starfleet officer who rescued Worf had been told by the Klingon government that he had no living relatives, but Kurn was taken in by his father's closest friend, Lorgh, and raised as his son.
He had no living relatives. This was what the Starfleet officer who rescued Worf had been told by the Klingon government. Kurn was taken in by his father's closest friend. Kurn was raised as his son. Lorgh was his father's closest friend.