primogenitor vs antecedent

primogenitor and antecedent both are nouns.

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

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

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

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

primogenitor (noun)	antecedent (noun)
an ancestor in the direct line	the referent of an anaphor; a phrase or clause that is referred to by an anaphoric pronoun
	a preceding occurrence or cause or event
	someone from whom you are descended (but usually more remote than a grandparent)
	anything that precedes something similar in time

primogenitor (adjective)	antecedent (adjective)
	preceding in time or order