Gaius Julius Caesar most commonly known as Gaius Caesar or Caius Caesar, was the oldest son of Marcus Vipsanius Agrippa

Marcus Vipsanius Agrippa

Marcus Vipsanius Agrippa was a Roman statesman and general. He was a close friend, son-in-law, lieutenant and defense minister to Octavian, the future Emperor Caesar Augustus...

 and Julia the Elder

Julia the Elder

Julia the Elder , known to her contemporaries as Julia Caesaris filia or Julia Augusti filia was the daughter and only biological child of Augustus, the first emperor of the Roman Empire. Augustus subsequently adopted several male members of his close family as sons...

. He was born between 14 August and 13 September 20 BC or according to other sources in 23 September 20 BC with the name Gaius Vipsanius Agrippa, but when he was adopted by his maternal grandfather Roman Emperor

Roman Emperor

The Roman emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office although at any given time, a given title was associated with the emperor...

 Augustus

Augustus

Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

, his name was changed to Gaius Julius Caesar.
Gaius was adopted along with his brother Lucius Caesar

Lucius Caesar

Lucius Julius Caesar , most commonly known as Lucius Caesar, was the second son of Marcus Vipsanius Agrippa and Julia the Elder. He was born between 14 of June and 15 July 17 BC with the name Lucius Vipsanius Agrippa, but when he was adopted by his maternal grandfather Roman Emperor Caesar...

 in 17 BC by their maternal grandfather, the Roman Emperor

Roman Emperor

The Roman emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office although at any given time, a given title was associated with the emperor...

 Augustus

Augustus

Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

, who named the two boys his heirs.