One of his second cousins was the dictator Julius Caesar, the great-grandson of another Quintus Marcius Rex, the praetor in 144 BC who constructed the Aqua Marcia.
Metellus died near the start of the year, and, although Servilius Vatia was elected to replace him, Vatia died before he could enter office and Marcius continued as sole consul.
[1] Marcius went to serve in Cilicia as proconsul and, pressured by his brother-in-law, Publius Clodius, refused to help Lucius Licinius Lucullus.
He was still waiting outside the city for a triumph when the Catilinarian Conspiracy broke out in 63 BC.
Marcius had married, Clodia Tertia, a sister of Publius Clodius Pulcher.