Sven Estridsson
According to Adam of Bremen, the mother of King Olav Kyrre remarried either King Sweyn II of Denmark or an unnamed Swedish king (possibly King Haakon of Sweden) as a widow, but this is unconfirmed. It is also unknown whether this refers to the actual mother of Olav Kyrre, which would mean Tora Torbergsdatter, or his stepmother, which would mean Elisiv.