Ancestors: the people from whom one is descended; forefathers and foremothers of a family line.
お盆には先祖の墓参りをします。
During Obon we visit our ancestors' graves.
先祖から受け継いだ土地を守りたいと思う。
I want to protect the land inherited from my ancestors.
家系図を作って先祖を調べた。
I made a family tree to research my ancestors.