1One's ancestors; the people from earlier generations of one's family line to whom one is related by blood.
お盆には先祖のお墓参りをする習慣がある。
There is a custom of visiting ancestors' graves during Obon.
先祖代々受け継がれてきた土地だ。
This is land that has been passed down from ancestor to ancestor.
家系図を調べて先祖のことを知った。
I researched my family tree and learned about my ancestors.
この家は先祖が武士だったそうだ。
I heard that this family's ancestors were samurai.