stepfather vs father figure

stepfather and father figure both are nouns.

Word	Noun	Adjective	Verb	Adverb
stepfather	Yes	No	No	No
father figure	Yes	No	No	No

As nouns, father figure is a hypernym of stepfather; that is, father figure is a word with a broader meaning than stepfather:

Other hypernyms of stepfather include father surrogate, stepparent.

stepfather (noun)	father figure (noun)
the husband of your mother by a subsequent marriage	a man who takes over all the functions of the real father