Generally, a midaidokoro came from a court noble family, a house of an imperial prince or the Imperial family (there were two exceptions, Kodaiin and Tenshoin, midaidokoro of the 11th Shogun Ienari TOKUGAWA, although they came from the Shimazu family, they were adopted by the house of Konoe, and then married with the shogun).
御台所は、公家･宮家･天皇家から迎えるのが慣例となっていた（例外は、11代将軍徳川家斉御台所･広大院と天璋院の2人で、どちらも島津家出身であったが、近衛家に養女となった上で輿入れした）。