quadruplet vs sib

quadruplet and sib both are nouns.

Word	Noun	Adjective	Verb	Adverb
quadruplet	Yes	No	No	No
sib	Yes	No	No	No

As nouns, sib is a hypernym of quadruplet; that is, sib is a word with a broader meaning than quadruplet:

quadruplet: one of four children born at the same time from the same pregnancy
sib: a person's brother or sister

Other hypernyms of quadruplet include sibling.

quadruplet (noun)	sib (noun)
a set of four similar things considered as a unit	one related by blood or origin; especially on sharing an ancestor with another
one of four children born at the same time from the same pregnancy	a person's brother or sister
the cardinal number that is the sum of three and one