John Castle (born 14 January 1940) is an English actor.
 Castle has acted in theatre, film and television.
 He is known for his role as Agrippa Postumus in the BBC television adaptation of "I, Claudius" (1976) and for playing Geoffrey II, Duke of Brittany, in the film "The Lion in Winter" (1968).
 He also played Dr Carrasco as well as the prisoner called "The Duke" in the film "Man of La Mancha" (1972), and the villainous Paul McDagget in "RoboCop 3" (1993).
Vipsania Marcella Agrippina or Marcellina or Vipsania Tertia (born 27 BC or later) was perhaps the only daughter of Roman statesman Marcus Vipsanius Agrippa by his second wife Claudia Marcella Major.
 If so, she was the first grandchild to Octavia Minor and first great-niece to Roman Emperor Augustus.
 If she truly had the name Marcella, there is no way that she was a daughter of Agrippa's first wife, Caecilia Attica.
 She and her elder sisters Vipsania Agrippina were married off to Q. Haterius (cos. 5 BC), Publius Quinctilius Varus (cos. 13 BC) and Tiberius (also cos. 13 BC) respectively.
 Nepos "Att".
 19 records the birth of Tiberius's future wife before the death of Atticus.
 She and Haterius had a son, Q. Haterius Agrippa, who was consul in AD 22 at a youthful age (probably the legal minimum 33 with a ten-year dispensation as a grandson of Agrippa).
Agrippa Postumus (26 June 12 BC – 20 August AD 14), also referred to as Postumus Agrippa, was a son of Marcus Vipsanius Agrippa and Julia the Elder.
 He was originally named Marcus Vipsanius Agrippa Postumus in honor of his father, who died shortly before Postumus' birth.
 After the deaths of his older brothers, Lucius (d. AD 2) and Gaius Caesar (d. AD 4), Postumus was adopted by his maternal grandfather, the Roman emperor Augustus.
 In accordance with Roman naming conventions, Postumus' name was changed to Marcus Julius Caesar Agrippa Postumus.
 At the time Augustus considered Postumus as a potential successor, but banished him from Rome in 9AD, for reasons that remain unknown.
 This, in effect, though not in law, cancelled his adoption and virtually assured Tiberius' position as Augustus' sole heir.
 Postumus was ultimately executed by his own guards shortly after Augustus' death in AD 14.
Sempronius Gracchus was a Roman nobleman who seduced Julia the Elder when she was wife of Marcus Agrippa; this led to a long-term affair.
 Gracchus was involved in an intrigue with the imperial family of Augustus by which he sought to undermine the position of Tiberius.
 He was married to a woman called Alliaria.
 His affair was discovered by Augustus who banished him to Cercina (Kerkennah Islands) where he endured an exile of fourteen years.
 Most probably he was executed in AD 14 on the orders of Tiberius after his accession.
Vibulenus Agrippa (called Vibullius Agrippa in Dio's "Roman History") was a Roman knight of the Equestrian rank who was accused of some crime, probably treason, before the senate in the final years of the reign of Tiberius, in 36 AD.
 His case is often mentioned to highlight the frequency with which ordinary citizens were being executed in that time, and for the novelty of the case's outcome: Vibulenus faced his accusers in the senate and swallowed poison that he had brought with him in a ring.
Marcus Vipsanius Agrippa ( ; 64/62 BC – 12 BC) was a Roman consul, statesman, general and architect.
 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.
 As a result of these victories Octavian became the first Roman Emperor, adopting the name of Augustus.
 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.
 He was responsible for the creation of many baths, porticoes and gardens, as well as the original Pantheon.
 Agrippa was also father-in-law to the second Emperor Tiberius, maternal grandfather to Caligula, and maternal great-grandfather to the Emperor Nero.
Decimus or Didius Haterius Agrippa was the son of the orator and senator Quintus Haterius.
 He was tribune of the plebs in AD 15 and vetoed proposals; was praetor in 17, consul in 22, and senator from 15 on.
 Agrippa at one time strongly urged the emperor Tiberius to nominate a limited number of political candidates from each family.
 He died in 32, a victim of Tiberius' reign of terror.
 He is not to be confused with Postumus Agrippa, a kinsman (half-uncle).
Gaius Rubellius Plautus (33–62 AD) was a Roman noble and a political rival of Emperor Nero.
 Through his mother Julia, he was a relative of the Julio-Claudian dynasty.
 He was the grandson of Drusus (only son of Tiberius Caesar), and the great-grandson of Tiberius and his brother Drusus.
 Through his great-grandmothers Vipsania Agrippina and Antonia Minor, he was also descended from Marcus Vipsanius Agrippa and Mark Antony but not from Augustus.
 He was descended from Augustus' sister Octavia Minor, herself a great niece of Julius Caesar.
Tiberius (Latin: "Tiberius Caesar Dīvī Augustī Fīlius Augustus" ; 16 November 42 BC – 16 March 37 AD) was a Roman emperor from 14 AD to 37 AD.
 Born Tiberius Claudius Nero, a Claudian, Tiberius was the son of Tiberius Claudius Nero and Livia Drusilla.
 His mother divorced Nero and married Octavian, later known as Augustus, in 39 BC, making him a step-son of Octavian.
Lucius Apronius was a Roman military commander active during the reign of Tiberius.
 Apronius shared in the achievements of Vibius Postumus and earned the ornaments of a triumph for his distinguished valor in Dalmatian revolt and Germanic Wars, along with Aulus Caecina Severus and Gaius Silius in 15 AD.
 In the Senate, Apronius in 22 procured a decree of votive offerings should be made, due to the successful prosecution of Gnaeus Calpurnius Piso, who had engaged in subversive plotting against Tiberius.

Question: what does Agrippa Postumus and Tiberius have in common?
Answer: son