The emperor Diocletian was known for his horrific treatment of Catholics. From 303-311 AD, he was responsible for the persecution and murder of scores of people. This ended with the accession of Constantine I, the Great, who was a Catholic. More damaging to his legacy, the tetrarchy suffered a collapse shortly after Diocletian had retired. Constantine I was born to Helena and Constantius Chlorus, a Roman emperor of the west (with Galerius as ruler in the east). Constantius Chlorus was the patriarch of the Family of Constantine. His father became a part of the tetrarchy under the emperor Diocletian.  Diocletian was one of the most effective emperors of the changing Roman empire. He is probably best known for his halt of the 3rd century chaos that overwhelmed the empire. He also established the short lived government rule of a tetrarchy. The tetrarchy distributed power equally among four co-rulers in four frontier cities of the empire. Specifically these were Nicomedia, Mediolanum, Antioch and Trier. More notably it took the leadership role from the decaying city of Rome and paved the way for the new capital of Constantinople in the eastern empire. He took as his co-rulers Maximian, his fellow officer, as co-emperor (in 286 AD) and as junior co-emperors Galerius and Constantius (in 293 AD). Diocletian also made the Roman empire the most bureaucratic in its existence. He did this by expanding civil and military services, as well as placing more emphasis on distribution of power in the newly formed administrative districts. Diocletian was the first Roman emperor to step down from power.

When he became affiliated with Diocletian, Constantius Chlorus left Helena in order to marry Theodora, the step-daughter (although this is disputed) of Diocletian’s co-ruler Maximian. Some suggest that Helena was merely a concubine of Constantius Chlorus. Whatever the case, Constantine was the only child born between his parents. Constantius Chlorus ended up having six children with his second wife.  His relationship with his son Constantine remained strong throughout their lives and he became his  father's heir apparent and was settled into Diocletian’s court in Nicomedia. 

With the death of Constantius, the tetrarchy was further fractured and resulted in a change in leadership. Constantine’s early rule was only accepted because the new ruler Galerius felt threatened by him. There was much political intrigue taking place during the period when Constantine I became a caesar. This seat greatly disturbed the remaining tetrarchy and eventually Maxentius, son of Maximian, rebelled against Constantine. In the interim Maximian even came out of retirement and had his daughter Fausta married to Constantine in order to settle the waters. 

Maxentius and Constantine never harmoniously ruled together and the conflict culminated at the famous Battle at the Milvian Bridge on October 28, 312. The result was Constantine’s victory, eventual dismantling of the tetrarchy and finally sole rule of the Roman world. Constantine is also known for his religious tolerance and ending persecution of Christians. His mother Helena was revered for her devotion to Christianity.