Wikipedia
Theoclia (flourished 3rd century, died 218) was a Syrian Roman noblewoman.
Theoclia was most probably born and raised in Arca Caesarea (modern Arqa, Lebanon). She is the known daughter of the Roman Equestrian Promagistrate Marcus Julius Gessius Marcianus and his wife, Julia Avita Mamaea. She is the known sister of the Roman emperor Alexander Severus, who ruled from 222 until 235. She may had an elder brother called Marcus Julius Gessius Bassianus who served as a Magister (master) in the Arval Brethren during the reign of Roman emperor Caracalla who ruled from 212 until 217.
Through her mother, Theoclia was a relation to the Royal family of Emesa and the Severan dynasty of the Roman Empire. The only two Roman Historical sources that mention her is Roman History by Cassius Dio who mentions Theoclia as only the unnamed sister of Alexander Severus and the Augustan History book The Two Maximini who gives her name as Theoclia.
Mamaea intended at one time for Theoclia to marry Gaius Julius Verus Maximus, son of the future Roman emperor Maximinus Thrax from wife, Caecilia Paulina. However Alexander Severus, persuaded his mother not to marry Theoclia to Maximus disliking the moroseness of Maximus’ father. Instead, Mamaea married Theoclia to a Roman nobleman of illustrious birth called Messalla. The Augustan History describes Theoclia’s character as a 'product of Greek culture' while describes her husband Messalla as a learned man who was a very powerful speaker. Theoclia, along with her husband and father were murdered on the orders of Roman emperor Macrinus in 218 in Emesa, Syria.