male sibling vs brother

male sibling and brother both are nouns.

Word	Noun	Adjective	Verb	Adverb
male sibling	Yes	No	No	No
brother	Yes	No	No	No

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

Other hyponyms of male sibling include blood brother.

male sibling (noun)	brother (noun)
a sibling who is male	a male with the same parents as someone else
	a male person who is a fellow member (of a fraternity or religion or other group)
	a close friend who accompanies his buddies in their activities
	used as a term of address for those male persons engaged in the same movement