royal house vs royalty

royal house and royalty both are nouns.

Word	Noun	Adjective	Verb	Adverb
royal house	Yes	No	No	No
royalty	Yes	No	No	No

As nouns, royal house and royalty are synonyms defined as:

Other synonyms of royal house include royal family, royal line.

royal house (noun)	royalty (noun)
royal persons collectively	royal persons collectively
	payment to the holder of a patent or copyright or resource for the right to use their property