Childhood and family
He was born as the only child of Titus Aurelius Fulvus, consul in 86, whose family came from Nemausus (modern Nîmes). Titus Aurelius Fulvius was the son of a senator of the same name, who, as legate of Legio III Gallica, had supported Vespasian in his bid to the Imperial office and been rewarded with a suffect consulship, plus an ordinary one under Domitian in 85. The Aurelii Fulvii were therefore a relatively new senatorial family from Gallia Narbonensis whose rise to prominence was supported by the Flavians. The link between Antoninus' family and their home province explains the increasing importance of the post of Proconsul of Gallia Narbonensis during the late Second Century.
Antoninus was born near Lanuvium and his mother was Arria Fadilla. Antoninus’ father died shortly after his 89 ordinary consulship, and Antoninus was raised by his maternal grandfather Gnaeus Arrius Antoninus, reputed by contemporaries to be a man of integrity and culture and a friend of Pliny the Younger. The Arrii Antoninii were an older senatorial family from Italy, very influential during Nerva's reign. Arria Fadilla, Antoninus' mother, married afterwards Publius Julius Lupus, suffect consul in 98; from that marriage came two daughters, Arria Lupula and Julia Fadilla.
Marriage and children
Some time between 110 and 115, Antoninus married Annia Galeria Faustina the Elder. They are believed to have enjoyed a happy marriage. Faustina was the daughter of consul Marcus Annius Verus and Rupilia Faustina (a half-sister to the Empress Vibia Sabina). Faustina was a beautiful woman, and despite (basically unproven) rumours about her character, it is clear that Antoninus cared for her deeply.
Faustina bore Antoninus four children, two sons and two daughters. They were:
- Marcus Aurelius Fulvus Antoninus (died before 138); his sepulchral inscription has been found at the Mausoleum of Hadrian in Rome.
- Marcus Galerius Aurelius Antoninus (died before 138); his sepulchral inscription has been found at the Mausoleum of Hadrian in Rome. His name appears on a Greek Imperial coin.
- Aurelia Fadilla (died in 135); she married Lucius Plautius Lamia Silvanus, consul 145. She appeared to have no children with her husband; and her sepulchral inscription has been found in Italy.
- Annia Galeria Faustina Minor or Faustina the Younger (between 125–130–175), a future Roman Empress, married her maternal cousin Marcus Aurelius in 146.
When Faustina died in 141, Antoninus was greatly distressed. In honour of her memory, he asked the Senate to deify her as a goddess, and authorised the construction of a temple to be built in the Roman Forum in her name, with priestesses serving in her temple. He had various coins with her portrait struck in her honor. These coins were scripted ‘DIVA FAUSTINA’ and were elaborately decorated. He further created a charity which he founded and called it Puellae Faustinianae or Girls of Faustina, which assisted destitute girls  of good family. Finally, Antoninus created a new alimenta (see Grain supply to the city of Rome).
The emperor never remarried. Instead, he lived with Galena Lysistrata, one of Faustina's freed women. Concubinage was a form of female companionship sometimes chosen by powerful men in Ancient Rome, especially widowers like Vespasian, and Marcus Aurelius. Their union could not produce any legitimate offspring who could threaten any heirs, such as those of Antoninus. Also, as one could not have a wife and an official concubine (or two concubines) at the same time, Antoninus avoided being pressed into a marriage with a noblewoman from another family (later, Marcus Aurelius would also reject the advances of his former fiancée Ceionia Fabia, Lucius Verus's sister, on the grounds of protecting his children from a stepmother, and took a concubine instead).
Favor with Hadrian
Having filled the offices of quaestor and praetor with more than usual success, he obtained the consulship in 120. He was next appointed by the Emperor Hadrian as one of the four proconsuls to administer Italia, then greatly increased his reputation by his conduct as proconsul of Asia, probably during 134–135.
He acquired much favor with Hadrian, who adopted him as his son and successor on 25 February 138, after the death of his first adopted son Lucius Aelius, on the condition that Antoninus would in turn adopt Marcus Annius Verus, the son of his wife's brother, and Lucius, son of Lucius Aelius, who afterwards became the emperors Marcus Aurelius and Lucius Verus.