quintuplet vs sib

quintuplet and sib both are nouns.

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

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

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

Other hypernyms of quintuplet include sibling.

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