Complex sentence: Valdemar was the son of princess Ingeborg Eriksdotter of Sweden and Birger jarl, from the House of Bjelbo, who more or less ruled Sweden from 1248 under King Eric XI of Sweden.
Split into simpler sentences: Valdemar was the son of princess Ingeborg Eriksdotter of Sweden and Birger jarl, from the House of Bjelbo. Birger Jarl more or less also ruled Sweden from 1248 under King Eric XI of Sweden.