Alexander Severus in the context of "Legio IV Italica"

John Xiphilinus or Joannes Xiphilinos (Greek: Ἰωάννης Ξιφιλῖνος), epitomator of Dio Cassius, lived at Constantinople during the latter half of the 11th century AD. He was a monk and a member of the Xiphilinus family, a nephew of Patriarch John VIII of Constantinople, a well-known preacher (Migne, Patrologia Graeca, cxx.).

The epitome of Dio was prepared by order of Michael Parapinaces (1071–1078), but is incomplete. It comprises books 36–80, the period included being from the times of Pompey and Caesar down to Alexander Severus. In book 70 the reign of Antoninus Pius and the early years of Marcus Aurelius appear to have been missing in his copy, while in books 78 and 79 a mutilated original must have been used. Xiphilinus divided the work into sections, each containing the life of an emperor. He omitted the names of the consuls and sometimes altered or emended the original. The epitome is valuable as preserving the chief incidents of the period for which the authority of Dio is wanting.

Julia Avita Mamaea or Julia Mamaea (14 or 29 August around 182 – March 21/22 235) was a Syrian noble woman and member of the Severan dynasty. She was the mother of Roman emperor Alexander Severus and remained one of his chief advisors throughout his reign. She was killed in 235 by rebel soldiers alongside her son.

Julius Bassianus (born in the second half of the 2nd century, died 217) was an Arab high priest of Elagabalus at the Temple of the Sun in Emesa, Syria, where this solar deity was worshipped in a shape of a black stone. The name Elagabalus derives from Ilāh (a Semitic word for "god") and gabal (an Arabic word for "mountain"), resulting in "the God of the Mountain," the Emesene manifestation of the deity. Bassianus was a member of the Royal family of Emesa (modern Homs), which was a part of the Arab aristocracy in this client kingdom of the Roman Empire. The beginning of his priesthood is unknown, but by 187 he was a high priest at Emesa. Bassianus was a son of a Julius and his paternal uncle was Julius Agrippa, who served as a Primipilaris (a former leading Centurion).

Future emperor Lucius Septimius Severus had visited Emesa, based on a promising horoscope that he would find his future wife in Syria. Bassianus introduced Severus to his two daughters. Bassianus' wife is unknown. His elder daughter Julia Maesa was married to a Syrian noble Gaius Julius Avitus Alexianus and they had two daughters: Julia Soaemias Bassiana and Julia Avita Mamaea. His younger daughter Julia Domna was not married. Severus and Domna married not so long after. Domna bore Severus two sons, Lucius Septimius Bassianus (Caracalla, 4 April 188-8 April 217) and Publius Septimius Geta (7 March 189-19 December 211). Caracalla and Geta would become future Roman Emperors and heirs to their father. After Caracalla's death, Julia Maesa's grandson became emperor, Elagabalus. She prevailed upon him to adopt another grandson of her, the son of Julia Avita Mamaea, who took the name Alexander Severus. Eventually the latter became emperor himself.

Herennius Modestinus, or simply Modestinus, was a civil servant and a celebrated Roman jurist, a student of Ulpian who flourished about 250 AD.

He appears to have been a native of one of the Greek-speaking provinces, or probably Dalmatia. Possibly from 223 to 225 AD he was secretary a libellis under Emperor Alexander Severus, and about 228 he was praefectus vigilum.In Valentinian's Law of Citations he is classed with Papinian, Paulus, Gaius and Ulpian, as one of the five jurists whose recorded views were considered decisive. He is considered to be the last great jurist of the classic age of Roman law.

Julius Paulus (Greek: Ἰούλιος Παῦλος; fl. 2nd century and 3rd century AD), often simply referred to as Paul in English, was one of the most influential and distinguished Roman jurists. He was also a praetorian prefect under the Roman Emperor Alexander Severus.

Pope Callixtus I (Greek: Κάλλιστος), also called Callistus I, was the bishop of Rome (according to Sextus Julius Africanus) from c. 218 to his death c. 222 or 223. He lived during the reigns of the Roman emperors Elagabalus and Alexander Severus. Eusebius and the Liberian catalogue list his episcopate as having lasted five years (217–222). In 217, when Callixtus followed Zephyrinus as Bishop of Rome, he started to admit into the Church converts from sects or schisms. He was killed for being Christian and is venerated as a saint and martyr by the Catholic Church (the patron saint of cemetery workers).