love child vs offspring

love child and offspring both are nouns.

Word	Noun	Adjective	Verb	Adverb
love child	Yes	No	No	No
offspring	Yes	No	No	No

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

Other hypernyms of love child include issue, progeny.

love child (noun)	offspring (noun)
the illegitimate offspring of unmarried parents	any immature animal
	something that comes into existence as a result
	the immediate descendants of a person