Synonyms for Sextet (same or very similar meaning)
WordNet sense 1 (the cardinal number that is the sum of five and one):
sextuplet, six, hexad, sestet, sise, sixer, VI, Captain Hicks, half a dozenWordNet sense 2 (six performers or singers who perform together):
sextetteWordNet sense 3 (six people considered as a unit):
sixsomeFrom the ODE community, based on WordNetadd/edit