Complex sentence: Before 1170, Birger was married to Birgit Haraldsdotter, the daughter of the Norwegian king Harald Gille, and who had formerly been married to the Danish impostor Magnus Henriksson, who ruled in Uppsala 1160-1161.
Split into simpler sentences: Before 1170, Birger was married to Birgit Haraldsdotter, the daughter of the Norwegian king Harald Gille. She had formerly been married to the Danish impostor Magnus Henriksson, who had briefly ruled in Uppsala 1160-1161.