Fabius Maximus Allobrogicus was the son of Quintus Fabius Maximus Aemilianus, the Roman consul of 145 BC, and a member of the patrician "gens Fabia". His first appearance was during the elections for quaestor in 134 BC; he was recommended to the voters as a candidate by his biological uncle Scipio Aemilianus, and after Allobrogicus was elected, Scipio took him as his quaestor to Hispania Citerior where they fought in the Second Numantine War. While there, Allobrogicus was placed in charge of 4,000 volunteers.