forefather vs sire

forefather and sire both are nouns.

Word	Noun	Adjective	Verb	Adverb
forefather	Yes	No	No	No
sire	Yes	No	Yes	No

As nouns, forefather and sire are synonyms defined as:

Other synonyms of forefather include father.

forefather (noun)	sire (noun)
the founder of a family	male parent of an animal especially a domestic animal such as a horse
person from an earlier time who contributed to the tradition shared by some group	the founder of a family
	a title of address formerly used for a man of rank and authority

forefather (verb)	sire (verb)
	make (offspring) by reproduction