sib vs quintuplet

sib and quintuplet both are nouns.

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

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

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

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

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