inbreeding vs sexual union

inbreeding and sexual union both are nouns.

Word	Noun	Adjective	Verb	Adverb
inbreeding	Yes	No	No	No
sexual union	Yes	No	No	No

As nouns, sexual union is a hypernym of inbreeding; that is, sexual union is a word with a broader meaning than inbreeding:

inbreeding: the act of mating closely related individuals
sexual union: the act of pairing a male and female for reproductive purposes

Other hypernyms of inbreeding include conjugation, coupling, mating, pairing, union.

inbreeding (noun)	sexual union (noun)
the act of mating closely related individuals	the act of pairing a male and female for reproductive purposes