先せん々せん代だい

noun, noun which may take the genitive case particle 'no'

the one before last; two generations previous

Refers to the person or thing two positions back in a generational or sequential context, such as a company president, family head, or title holder. Often used with 社長, 会長, 当主, etc.

• 先々せんせん代だいの社しゃ長ちょうが築きずいた方ほう針しんを今いまも守まもっている。

  We still follow the policies established by the president two generations ago.

• この茶ちゃ碗わんは先々せんせん代だいから伝つたわる家か宝ほうだ。

  This tea bowl is a family heirloom passed down from two generations back.