How was Fridlevus II related to Halfdan?
Fridlevus II Fridleif (Ynglinga saga) was a son of Fróði of the Skjöldung (Scylding) lineage. In that work he was the brother of Halfdan and the father of Áli the Strong.
Frederick V of Denmark Frederick V (Danish and Norwegian: "Frederik"; 31 March 172314 January 1766) was king of Denmark-Norway and Duke of Schleswig-Holstein from 1746 until his death. He was the son of Christian VI of Denmark and Sophia Magdalene of Brandenburg-Kulmbach.