'Ancestor's' in the Bible

"Send men to explore the land of Canaan that I'm about to give to the Israelis. Send one man to represent each of his ancestor's tribes, every one of them a distinguished leader among them."

but the land is to be divided by lot, inheriting according to the names of their ancestor's tribe.

They married into families of the descendants of Manasseh, that is, Joseph's descendants, so that their inheritance remained within the tribe of their ancestor's family.