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.
Second Swedish Crusade The Second Swedish Crusade was a Swedish military expedition to areas in present-day Finland by Birger Jarl in the 13th century. As a result of the crusade, the Swedish kingdom began to exert influence in western Finland.