heir vs offspring

heir and offspring both are nouns.

Word	Noun	Adjective	Verb	Adverb
heir	Yes	No	No	No
offspring	Yes	No	No	No

As nouns, offspring is a hypernym of heir; that is, offspring is a word with a broader meaning than heir:

Other hypernyms of heir include issue, progeny.

heir (noun)	offspring (noun)
a person who is entitled by law or by the terms of a will to inherit the estate of another	any immature animal
a person who inherits some title or office	something that comes into existence as a result
	the immediate descendants of a person