brother vs blood brother

brother and blood brother both are nouns.

Word	Noun	Adjective	Verb	Adverb
brother	Yes	No	No	No
blood brother	Yes	No	No	No

As nouns, brother and blood brother are synonyms defined as:

brother (noun)	blood brother (noun)
a male with the same parents as someone else	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 male sworn (usually by a ceremony involving the mingling of blood) to treat another as his brother
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