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.
Prince Waldemar of Schaumburg-Lippe Prince Waldemar Stephen of Schaumburg-Lippe ("Waldemar Stephan Ferdinand Wolrad Friedrich Karl", b. 19 December 1940 in Glienicke) is a son of Prince Christian of Schaumburg-Lippe and Princess Feodora of Denmark, and the great-grandson of King Frederick VIII of Denmark.