primogenitor vs ancestor

primogenitor and ancestor both are nouns.

Word	Noun	Adjective	Verb	Adverb
primogenitor	Yes	No	No	No
ancestor	Yes	No	No	No

As nouns, ancestor is a hypernym of primogenitor; that is, ancestor is a word with a broader meaning than primogenitor:

primogenitor: an ancestor in the direct line
ancestor: someone from whom you are descended (but usually more remote than a grandparent)

Other hypernyms of primogenitor include antecedent, ascendant, ascendent, root.

primogenitor (noun)	ancestor (noun)
an ancestor in the direct line	someone from whom you are descended (but usually more remote than a grandparent)