Constantius I Chlorus in Wikipedia

Flavius Valerius Constantius[2] (c. 31 March 250 – 25 July 306), commonly known as Constantius I or Constantius Chlorus[3], was Roman Emperor from 293 to 306. He was the father of Constantine the Great and founder of the Constantinian dynasty. Life The Historia Augusta says Constantius was the son of Eutropius, a noble from northern Dardania in modern Serbia, and Claudia, a niece of the emperors Claudius II and Quintillus.[4] Modern historians suspect this maternal connection to be a genealogical fabrication created by his son Constantine I. His father, however, might have been the brother of Eutropia, wife of Maximian. Constantius was a member of the Protectores Augusti Nostri under emperor Aurelian and fought in the east against the secessionist Palmyrene Empire. Shortly after he attained the rank of tribunus within the army, and during the reign of Carus he was raised to the position of praeses, governor, of the province of Dalmatia.[5] In 293 the emperor Diocletian created the Tetrarchy, dividing the Roman Empire into Western and Eastern portions. Each would be ruled by an Augustus, supported by a Caesar. Diocletian became Augustus of the Eastern empire, with Galerius as his Caesar. Constantius was appointed Caesar to the Western Augustus, Maximian, and married Theodora, Maximian's stepdaughter. They had six children. Constantius divorced his first wife (or concubine), Helena, by whom he already had a son, Constantine. Helena was probably from Nicomedia in Asia Minor.[6] He was given command of Gaul, Britain and possibly Hispania. In 293, Constantius defeated the forces of Carausius, who had declared himself emperor in Britain and northern Gaul in 286, near Bononia. Carausius was killed by his rationalis Allectus, who took command of Britain until 296, when Constantius sent Asclepiodotus, a prefect of the Praetorian Guard, to invade the island. Allectus was defeated and killed, and Roman rule in Britain restored.[7] Also in 296, Constantius fought a battle against the Alamanni at the city of Lingonae (Langres) in Gaul. He was shut up in the city, but was relieved by his army after six hours, and defeated the enemy.[8] He defeated them again at Vindonissa (Windisch, Switzerland),[9] thereby strengthening the defenses of the Rhine frontier. Diocletian and Maximian stepped down as co-emperors in 305, possibly due to Diocletian's poor health, and the Caesars, Constantius and Galerius, became co-emperors. Constantius ruled the western empire, Galerius the eastern. Severus and Maximinus Daia were appointed Caesars. Constantine, who had hoped to be a Caesar, joined his father's campaigns in Gaul and Britain.[10] Constantius died in Britain, at Eboracum (York), in 306, and Constantine was declared emperor by the army.[11] Legend - Christian legends - As the father of Constantine, a number of Christian legends have grown up around Constantius. Eusebius's Life of Constantine claims that Constantius was himself a Christian, although he pretended to be a pagan, and while Caesar under Diocletian, took no part in the emperor's persecutions.[12] His first wife, Helena, found the True Cross. British legends - Constantius's activities in Britain were remembered in medieval British legend. According to Geoffrey of Monmouth's History of the Kings of Britain (1136), Constantius was sent to Britain by the Senate after Asclepiodotus, here a British king, was overthrown by Coel of Colchester. Coel submitted to Constantius and agreed to pay tribute to Rome, but died only eight days later. Constantius married Coel's daughter Helena and became king of Britain. He and Helena had a son, Constantine, who succeeded to the throne of Britain when his father died at York eleven years later.[13] The identification of Helena as British had previously been made by Henry of Huntingdon,[14] but has no historical validity: Constantius had divorced Helena before he went to Britain.