sib vs quadruplet

sib and quadruplet both are nouns.

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

As nouns, quadruplet is a hyponym of sib; that is, quadruplet is a word with a more specific, narrower meaning than sib:

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

Other hyponyms of sib include half blood, quad, quin, quint, quintuplet, triplet, twin.

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