brother

sibling, sister

stepbrother, stepsister

cousin, kinsman, kinswoman, relation, relative

in-law

kissing cousin

blood, clan, family, folk, house, kindred, kinfolk (or kinfolks), kinsfolk, line, lineage, people, race, stock, tribe

friar, mendicant, monastic, monk, oblate

clergyperson, cleric, clerical, clerk, deacon, divine, dominie, ecclesiastic, high priest, minister, preacher, reverend

abbot, archbishop, archpriest, bishop, dean, diocesan, monsignor, pope, prelate, presbyter

churchman, clergyman, father, Holy Joe [slang], padre

abbé, curate, curé, parson, pastor, rector, shepherd, vicar

chaplain, confessor, sky pilot

evangelist, missionary, missioner, missionizer, revivalist

nun

abbess, anchoress (or ancress), cloistress [obsolete], conventual, mother superior, novice, prioress, Reverend Mother, religious, votary [archaic]

clergywoman, deaconess, high priestess, priestess

comrade

alter ego, amigo, buddy, chum, compadre, confidant, confidante, crony, familiar, friend, intimate, mate [chiefly British], musketeer, pal

acquaintance

associate, cohort, colleague, companion, fellow, hearty, hobnobber, partner, peer, sport

blood brother, main man, sister

abettor (also abetter), accomplice, ally, collaborator, confederate

pen pal

benefactor, supporter, sympathizer, well-wisher

friendly