He is best known for his lead role in Race to Witch Mountain. Alexander also composed a single entitled "Liv It Up (Teenage Wasteland)." The song is about his euro trip with his highschool friends. He also starred in the film Grown Ups 2 portraying Braden.
Ludwig is a student at the University of Southern California, where he is studying film, theatre, and entrepreneurship. His mother, Sharlene, is a former actress and his father, Harald, is a businesssman and Co-Chairman and Member of Strategic Advisory Committee of Lions Gate Entertainment, the distributor and one of the studios behind The Hunger Games.
Now he is best known for his acting in the History-Serie Vikings. Since season 2 he represents Bjorn Lothbrok, son of Ragnar and Lagertha. He is still appearing in season 3.
He will be in the upcoming film Lone Survivor.