Question: Which Roman Emperor was grandfather to the children of Mark Antony?

<P0-S0> Antonia Minor ("PIR" A 885), also known as Julia Antonia Minor, Antonia the Younger or simply Antonia (31 January 36 BC - September/October AD 37) was the younger of two daughters of Mark Antony and Octavia Minor. <P0-S1>  She was a niece of the Emperor Augustus, sister-in-law of the Emperor Tiberius, paternal grandmother of the Emperor Caligula and Empress Agrippina the Younger, mother of the Emperor Claudius, and both maternal great-grandmother and paternal great-aunt of the Emperor Nero. <P0-S2>  She was additionally the maternal great-aunt of the Empress Valeria Messalina and Faustus Cornelius Sulla Felix, the paternal grandmother of Claudia Antonia, Claudia Octavia, and Britannicus and the maternal grandmother of Julia Livia and Tiberius Gemellus. <SEP> <P1-S0> Marcus Vipsanius Agrippa ( ; 64/62 BC – 12 BC) was a Roman consul, statesman, general and architect. <P1-S1>  He was a close friend, son-in-law, and lieutenant to Octavian and was responsible for the construction of some of the most notable buildings in the history of Rome and for important military victories, most notably at the Battle of Actium in 31 BC against the forces of Mark Antony and Cleopatra. <P1-S2>  As a result of these victories Octavian became the first Roman Emperor, adopting the name of Augustus. <P1-S3>  Agrippa assisted Augustus in making Rome a city of marble and renovating aqueducts to give all Romans, from every social class, access to the highest quality public services. <P1-S4>  He was responsible for the creation of many baths, porticoes and gardens, as well as the original Pantheon. <P1-S5>  Agrippa was also father-in-law to the second Emperor Tiberius, maternal grandfather to Caligula, and maternal great-grandfather to the Emperor Nero. <SEP> <P2-S0> Claudia Marcella was the name of the two daughters of Octavia Minor, the sister of Roman emperor Augustus, by her first husband, the consul Gaius Claudius Marcellus. <P2-S1>  According to the Roman Historian Suetonius, they were known as The Marcellae sisters, and they are also known as the two Marcellae. <P2-S2>  The sisters were born in Rome. <P2-S3>  Between 40 BC-36 BC, they lived with their mother and their stepfather Triumvir Mark Antony in Athens, Greece. <P2-S4>  After 36 BC they accompanied their mother when she returned to Rome with their siblings. <P2-S5>  They were raised and educated by their mother, their maternal uncle, Roman emperor Augustus, and their maternal aunt-in-marriage Roman Empress Livia Drusilla. <P2-S6>  These two daughters of Octavia Minor and Gaius Claudius Marcellus with their siblings, provide a critical link between the past of the Roman Republic and the new Roman Empire. <P2-S7>  The marriages of the sisters and the children born to their unions assured republican family lines into the next generation. <SEP> <P3-S0> Caligula ( ), properly Gaius Julius Caesar Augustus Germanicus (31 August AD 12 – 24 January AD 41) was Roman emperor from AD 37–41. <P3-S1>  Born Gaius Julius Caesar Germanicus (not to be confused with Julius Caesar), Caligula was a member of the house of rulers conventionally known as the Julio-Claudian dynasty. <P3-S2>  Caligula's biological father was Germanicus, and he was the great-nephew and adopted son of Emperor Tiberius. <P3-S3>  The young Gaius earned the nickname "Caligula" (meaning "little soldier's boot", the diminutive form of "caliga", hob-nailed military boot) from his father's soldiers while accompanying him during his campaigns in Germania.