forefather       
noun [ C ]  literary uk/ˈfɔːˌfɑː.ðər/ us/ˈfɔːrˌfɑː.ðɚ/
 祖辈,祖亲
someone's relative who lived a long time ago
  Our forefathers fought for equal justice under the law. 我们的先辈曾为实现法律面前人人平等而抗争。 
 The house was built by his forefather William a hundred years before. 这所房子是他的祖先威廉爷爷在一百年前建的。 
 - More examples
 - Part of me is curious to explore what my forefathers believed in.
 - The values of our Victorian forefathers have served us well.
 - The descendants of General Tso have never heard of their forefather's infamous chicken dish.