Björn Kristian Ulvaeus (born 25 April 1945) is a Swedish musician, singer, songwriter, and producer best known as a member of the musical group ABBA. He is also the co-composer of the musicals Chess, Kristina från Duvemåla, and Mamma Mia! He co-produced the films Mamma Mia! and Mamma Mia! Here We Go Again with fellow ABBA member and close friend Benny Andersson. He is the oldest member of the group. Björn Kristian Ulvaeus was born in Gothenburg on 25 April 1945. In 1951, he moved with his family to Västervik, Kalmar County. His parents were Aina Eliza Viktoria (née Bengtsson; 1909–2005) and Erik Gunnar Ulvaeus (1912–1999). Ulvaeus has one sister, Eva Margareta (born 1948). Ulvaeus studied business and law at Lund University after undertaking his military service, alongside comedian Magnus Holmström. Before gaining international recogni...