sibling vs half blood

sibling and half blood both are nouns.

Word	Noun	Adjective	Verb	Adverb
sibling	Yes	No	No	No
half blood	Yes	No	No	No

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

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

sibling (noun)	half blood (noun)
a person's brother or sister	one of siblings who have only one parent in common