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.
Hálfdan Narfason Hálfdan Narfason (died 1568), was an Icelandic priest and Galdrmaster. He is known in Icelandic folklore, where he is the subject of many folksagas about his alleged magical performances.