three noble families (Kan'in, Kazan'in, Nakanoin or Koga)
Historical term referring to specific court noble lineages in the Heian period. The exact families may vary by context.
The three noble families of the Heian period included the Kan'in and Kazan'in lineages.
three branches of the Tokugawa family (Owari, Kii, Mito)
Historical term for the three collateral Tokugawa houses that could provide a shogunal heir. Compare with 御三家, which often refers to the same three families but can also be used figuratively.
See also: 御三家
The Tokugawa Gosanke refers to the three houses of Owari, Kii, and Mito.
three Tokugawa branch families; Gosanke · big three; top three
From 三 (three) + 家 (house/family). The specific families referred to depend on historical context.