同宗同源

tóngzōngtóngyuán
to share the same origins; to have common roots

CEDICT

Entry Composition

1 同宗 tóngzōng
  1. people who share common ancestry
  2. to be of the same clan; to have common ancestry
2 同源 tóngyuán
  1. homology (biology)
  2. a common origin