While I think the last two noble characters are up to discussion (jdellinger gave some fine examples), the two most virtuous members as described in the prologue are without question the parson and his brother the plowman. The parson is the only clergy member on the trip who does not indulge in money, food, drink, flesh, etc., and because of that is poor and must work harder. His brother, the plowman, is also described as being an extremely hard working laborer who prefers to earn his living honestly.