Erik Birgersson

Erik Birgersson (c. 1250 – 17 December 1275) was a Swedish duke from the House of Bjälbo (Folkungaätten) and the third son of Birger Jarl. His eldest brother, Valdemar, was elected King of Sweden, while his second brother, Magnus, was made a duke. Initially, Erik received no title, but later he and Magnus rebelled against King Valdemar. They defeated him at the Battle of Hova in 1275, after which Magnus was elected king and Erik took up his role as duke. However, he died shortly afterward.^[1][2] Erik may have had a genetic disorder known as Marfan syndrome.