Definition of brother :
1. A male person who has the same father and mother with another person, or who has one of them only. In the latter case he is more definitely called a half brother, or brother of the half blood.
2. One related or closely united to another by some common tie or interest, as of rank, profession, membership in a society, toil, suffering, etc.; - used among judges, clergymen, monks, physicians, lawyers, professors of religion, etc.
3. One who, or that which, resembles another in distinctive qualities or traits of character.
4. To make a brother of; to call or treat as a brother; to admit to a brotherhood.
accompaniment (part of speech: noun)
attachment, secondary, extra, companion, lieutenant, adornment, accessory, consort, appendage, accompaniment, extension, addition, appendix, addendum, garnish, ornament, second, adjunct, fixture, auxiliary, appurtenance
friend (part of speech: noun)
company, mate, fellow, confidant, acquaintance, friend, crony, comrade, classmate, chum, roommate, partner, intimate, teammate, amigo, co-worker, cousin, colleague, pal, schoolmate, playmate, buddy, ally, familiar
kinship (part of speech: noun)
flesh, maternity, relation, nephew, sisterhood, fatherhood, clan, kinship, paternity, ancestor, relative, heredity, lineage, fraternity, blood, mother, consanguinity, niece, kinfolk, family, kin, uncle, brotherhood, aunt, motherhood
clergy (part of speech: noun)
novice, pilgrim, abbess, pope, missionary, reverend, curate, clergyman, archdeacon, evangelist, nun, ecclesiastic, friar, minister, prioress, priest, father, canoness, vicar, sister, cleric, abbot, rector, archbishop, bishop, archpriest, prior, monk, prelate, chaplain, cardinal, pastor, canon, preacher