companion

colleague, coworker, equal, peer, workmate

accomplice, affiliate, ally, collaborator, confederate, half, partner

buddy, chum, confidant, familiar, friend, hearty, intimate, pal

countryman

classmate, housemate, messmate, playfellow, playmate, roommate (also roomie), schoolmate, shipmate, teammate

attendant, escort

hanger-on, leech, parasite

chaperone (or chaperon), squire

shadow, sidekick

conductor, leader, pilot

convoy, courier, honor guard, outrider

coordinate

coequal, counterpart, equal, equivalent, like, parallel, peer, rival

carbon copy, double, duplicate, facsimile, identical twin, likeness, mirror image, replica, ringer

analogue (or analog), similarity

accessory (also accessary), adjunct, appendage

complement, supplement

counterpart, fellow, mate

consequence, follow-up

fixings, trimmings