The first of Ysgramor’s Five Hundred Mighty Companions was actually two, the ashen-amalgamation of his sons that had survived Sarthaal only to die in the freeze-rains of the returning, named Tsunaltir and Stuhnalmir when alive and now called the Grit-Prince Tstunal, whose Tear-Wives were Vramali, Jarli-al, Alleir, and Tusk Widow Who Foreswore Her Name, whose Wine-Wives were Elja Hate-Basket and Ingridal who lost her casket at the burning, and Mjarili-al Half-Casket, whose Hearth-Wives were none survived, and whose Kyne-Wives were none survived, and whose Shield-Wives were Shanjenen the Echo-Eaten and Jahnsdotter Whose-Name-Stays-in-its-Cradle.
However, by the time Skyrim rolls around in 4E201, it's only possible to have one wife at a time. Does anyone know what caused this change in Nordic culture? What's the difference between the various types of wives, anyway?