Who is the son of Princess Märtha of Sweden and King Olav V?
Princess Märtha of Sweden: Princess Märtha of Sweden (Märtha Sofia Lovisa Dagmar Thyra; 28 March 1901 – 5 April 1954) was Crown Princess of Norway as the spouse of the future King Olav V from 1929 until her death in 1954. Princess Märtha of Sweden:  The presently reigning King Harald V is her only son. Olav V of Norway: Olav V (born Prince Alexander of Denmark; 2 July 1903 – 17 January 1991) was King of Norway from 1957 until his death.
King Harald V