attendant

accompanying, coincident, concomitant

contemporaneous, contemporary, simultaneous, synchronous

associated, collateral, connected, linked, related

consequent, resultant, resulting

ensuing, following, subsequent

accidental, casual, chance, fluky (also flukey), fortuitous, freak, incident, incidental

chaperone (or chaperon), squire

shadow, sidekick

conductor, leader, pilot

convoy, courier, honor guard, outrider

accessory (also accessary), adjunct, appendage

complement, supplement

counterpart, fellow, mate

consequence, follow-up

fixings, trimmings