sibling vs twin

sibling and twin both are nouns.

Word	Noun	Adjective	Verb	Adverb
sibling	Yes	No	No	No
twin	Yes	Yes	Yes	No

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

Other hyponyms of sibling include half blood, quad, quadruplet, quin, quint, quintuplet, triplet.

sibling (noun)	twin (noun)
a person's brother or sister	a duplicate copy
	either of two offspring born at the same time from the same pregnancy

sibling (adjective)	twin (adjective)
	being two identical

sibling (verb)	twin (verb)
	give birth to twins
	grow as twins
	bring two objects, ideas, or people together
	duplicate or match