Decius Caecilius belongs to a distinguished and powerful noble plebeian family. The Metellii favor the praenomen "Quintus", but he received, and passed on to his son, his unusual name after the Dioscuri (Castor and Pollux) appeared to his father in a dream just before a battle with the Samnites. He was ordered to name his oldest son "Decius" in return for victory.
At the time the series opens, he is a long-time widower with an adult son and at least two daughters. He is nicknamed "Cut-Nose" because he was slashed across the face with a sword while fighting under the command of Gaius Marius. He has served as Consul, and during the series becomes Censor. He is often impatient with his son whose behavior he often regards as beneath the dignity of his rank.