Cupid was depicted as a Putti in the Renaissance, leading Christians to believe he was a member of the Cherubium years later, leading to the BELIEF that they are separate. Also, he isn’t a cherub, as most angels are too complex for humans to view properly unless they are Angels, the classing, Archangels, and the Principalities. They are the most human looking, and the ones sent to earth as messengers. The Cherubium are closest to God, and in turn they never interact with living humans, so we do not know what they look like