五百年前是一家

wǔbǎiniánqiánshìyījiā
five hundred years ago we were the same family (saying) (said of persons with the same surname)

CEDICT

親戚關係很遠，但總有一點淵源。為同姓間互攀關係的用語。

重編國語辭典

Entry Composition

1 五百 wǔbǎi five hundred
2 年前 niánqián
  1. by the end of the year
  2. at the end of the year; shortly before New Year
=3 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=3 是 shì variant of 是 shì
4 一家 yījiā
  1. the whole family
  2. the same family
  3. the family ... (when preceded by a family name)
  4. group