Magnus III of Mecklenburg-Schwerin married the daughter of this monarch who reigned over which two countries?
Magnus III of Mecklenburg-Schwerin Magnus III of Mecklenburg (July 4, 1509 in Stargard – January 28, 1550 in Bützow) was a member of the House of Mecklenburg who was the first Lutheran administrator of the Prince-Bishopric of Schwerin, nevertheless referred to as prince-bishop. He was the son of Henry V, Duke of Mecklenburg and Ursula of Brandenburg. He was elected bishop in 1516, but due to his minority and lack of papal confirmation, he only began ruling as an administrator in 1532. He introduced the Reformation the next year. He married Elizabeth daughter of Frederick I of Denmark and Sophie of Pomerania. They had no children.
Charlotte of Naples Charlotte of Naples (  1479/1480 – 1506), also known as Charlotte of Aragon and Princess of Taranto, was the eldest daughter and eventual heiress of King Frederick of Naples. Although her father was dispossessed of his kingdom, her descendants, the House of La Trémoïlle maintained their dynastic claim in exile.