95 AD marked the fourteenth year of the reign of the Roman emperor Domitian. At 43 years of age (born in 51 AD), he was hardly an old man, but lifespans were short and death always close in the ancient world. Domitian himself had ascended the throne in 81 AD when his older brother Titus died unexpectedly of a fever at the age of 41.
Domitian, although married, had no surviving children. Nor did he have any surviving siblings. His father, the emperor Vespasian, had had only two children in addition to Domitian: Titus (39 AD - 81 AD) and a daughter, Flavia Domitilla the Younger (c. 45 AD - c. 66 AD). Domitian's nearest male relative and presumed successor in the event of his early death was Titus Flavius Clemens, the son of Vespasian's brother Titus Flavius Sabinus and thus Domitian's cousin.
Flavius Clemens's date of birth seems to be unknown, but assuming a date around 50 AD, he would have been about the same age as the emperor. Clemens apparently had his critics - in his Life of Domitian the historian Suetonius (c. 69 AD - c. 122 AD) describes Clemens as "a man of most contemptible laziness." But whatever his faults, Clemens retained the royal favor. He was permitted to marry his cousin Flavia Domitilla, the only daughter of Vespasian's deceased daughter Flavia Domitilla the Younger, who was thus Domitian's niece, and in 95 AD Domitian awarded him a prestigious ordinary consulship (that is, one that began at the start of the year) in 95 AD.
There is reason to believe that, in the longer term, Domitian was grooming two of the sons of Flavius Clemens and Flavia Domitilla to succeed him. Domitian apparently appointed the famed rhetorician Quintilian to tutor the boys, and Suetonius explicitly states that "Domitian had besides openly named [Clemens's] sons, who were then very young, as his successors, changing their former names and calling the one Vespasian and the other Domitian.
All of that ended abruptly at about the time that Clemens's consulship ended on May 1, 95. Domitian had Clemens executed, and exiled Clemens's widow to Pandateria. Why? Suetonius says only that Clemens was killed "suddenly and on a very slight suspicion," without specifying what the charges were. However, the historian Cassius Dio (c. 150 AD - 235 AD), writing some one hundred years later, asserts that Clemens and Domitilla were suspected of having converted to Judaism:
And the same year Domitian slew, along with many others, Flavius Clemens the consul, although he was a cousin and had to wife Flavia Domitilla, who was also a relative of the emperor's. The charge brought against them both was that of atheism, a charge on which many others who drifted into Jewish ways were condemned. Some of these were put to death, and the rest were at least deprived of their property. Domitilla was merely banished to Pandateria . . ..
Both the very unexpectedness of the charge and the fact that it does not fit the stereotyped Roman portrait of Domitian give it credibility. Roman historians, including both Suetonius and Dio, delighted in portraying Domitian as a jealous tyrant quick to act against any who insulted him or posed a threat, however trivial. Suetonius, for example, provides a laundry list of such victims, including Clemens's elder brother (and Domitian's cousin) Titus Flavius Sabinus, who was allegedly killed "because on the day of the consular elections the crier had inadvertently announced him to the people as emperor elect instead of consul:"
[Domitian] put to death many senators, among them several ex-consuls, including Civica Cerealis, at the very time when he was proconsul in Asia, Salvidienus Orfitus, Acilius Glabrio while he was in exile — these on the ground of plotting revolution, the rest on any charge, however trivial. He slew Aelius Lamia for joking remarks, which were reflections on him, it is true, but made long before and harmless. . . . He put to death Salvius Cocceianus, because he had kept the birthday of the emperor Otho, his paternal uncle; Mettius Pompusianus, because it was commonly reported that he had an imperial nativity and carried about a map of the world on parchment and speeches of the kings and generals from Titus Livius, besides giving two of his slaves the names of Mago and Hannibal; Sallustius Lucullus, governor of Britain, for allowing some lances of a new pattern to be named "Lucullean," after his own name; Junius Rusticus, because he had published eulogies of Paetus Thrasea and Helvidius Priscus and called them the most upright of men; and on the occasion of this charge he banished all the philosophers from the city and from Italy. He also executed the younger Helvidius, alleging that in a farce composed for the stage he had under the characters of Paris and Oenone censured Domitian's divorce from his wife; Flavius Sabinus too, one of his cousins, because on the day of the consular elections the crier had inadvertently announced him to the people as emperor elect, instead of consul.
The execution of Clemens presented the ancient historians with the perfect opportunity to portray Domitian, yet again, as a paranoid obsessed with uncovering insults and signs of usurpation. Their failure to do so strongly suggests that the charge was in fact something else.
Domitian's most careful modern biographer, Brian W. Jones, agrees that "Cassius Dio's comment on Clemens's atheism or adoption of Jewish ways should not be rejected out of hand." In his book The Emperor Domitian, Prof. Jones cites tantalizing hints in Jewish sources that suggest that Clemens may have at least been attracted to Judaism:
In Talmudic and Midrashic sources, reference is made to a Jewish proselyte named Onkelos, described as a son of Kalonikos or Kalonymos and as a nephew of Titus; on three occasions, the emperor tried to arrest him, but failed. In view of the vague similarity between Clemens and Kalonymos together with the reference to the imperial family, Cassius Dio's comment on Clemens's atheism or adoption of Jewish ways (67.14.2) should not be rejected out of hand. Furthermore, the Midrash and the Babylonian Talmud refer to a senator named Keti'ah bar Shalom who, converted with his wife to Judaism, was put to death by an emperor. All this is not hard evidence for the existence or extent of Clemens's sympathy with Judaism; probably it was only slight, but zealous delatores [informants] may well have found it enough to enable them to denounce him to the highly suspicious Domitian.
It remains to consider whether Clemens and Domitilla might have been attracted to Christianity rather than to Judaism. As you may be aware, Christians later claimed them as martyrs. Prof. Jones explains:
In the Christian tradition (i.e., the Acta of Saints Nereus and Achilleus), Domitilla and two of her eunuch servants, Nereus and Achilleus, were exiled to Terracina, where her servants were beheaded and she was burned to death. All three became official martyrs, with a feast day on 12 May (until 1969, when hers was abolished).
Nonetheless, the link to Christianity is doubtful. Dio, who was writing about 225 AD in Bithynia, "one of the most Christianized provinces of the Empire" (William H.C. Frend, The Early Church), specifically states that Clemens was associated with Judaism, not Christianity (although, as Prof Frend also points out, Dio "never mentions Christianity in his work"). The Roman Catacombs of Domitilla began as grant of land for her freedmen and did not become Christian until the mid to late 2nd Century. The story of her conversion smacks of legend with different versions of the story in circulation and changing over time. The Church historian Eusebius of Caesarea, for example, writing in the first third of the fourth century, characterizes Domitilla as Clemens's niece, not his wife, and has her banished to Pontia rather than to Pandateria or Terracina. ("[I]n the fifteenth year of Domitian Flavia Domitilla, daughter of a sister of Flavius Clement, who at that time was one of the consuls of Rome, was exiled with many others to the island of Pontia in consequence of testimony borne to Christ"). Finally, Prof. Jones reports that Clemens himself - as opposed to his wife - was first hailed as a Christian by George Syncellus (died after 810 AD) in the late 8th Century, some 700 years after Clemens's death.