Flavius Claudius Constantinus, born in Arelate ca.316, and made Caesar the same year. After the murder of Crispus in 325, Constantine II replaced him in administering Gaul though he was only 9. At his father's death he received the provinces of Gaul, Spain and Britain. Though this was a difficult area, it was perhaps seen as a tribute to him, since his father also started from this area. He had several successful campaigns against Germanic tribes.

As eldest son he was nominally in authority over the other two, but for practical purposes this doesn't seem to have had any bearing - they each ruled as independant emperors. In the spring of 340 he attempted to usurp Constan's rule in Italy, and was defeated and killed near Aquileia by Constan's troops.

Flavius Julius Constantius, born ca.317, and was made Caesar in 324. Constantine had sent Constantius east to take charge of the war against Sasanid Persia in 336. Upon the death of his father, he received the rule of the east from Cyrenaica (Libya) to Asia Minor. In 339 he also received Thrace from his brother Constans.

Constantius appeared to have strong preferences for the Arian religion, leading him into conflict with his more Orthodox brother Constans, though this never evolved into open warfare. At one point the western usurper Magnentius issued a series of coins featuring a large Christogram, in an apparent effort to raise support against Constantius.

Constantius made a temporary peace with the Sasanians in 350. Upon the death of Constans, Constantius defeated the western usurper in a series of battles, including at Mursa in the Balkans. Though most of the rest of the family had been massacred in the proscription following Constantine I's death, Constantius did receive help from two remaining relatives. Nepotian, a cousin, siezed Rome against Magnentius but didn't hold out long. Constantia, the sister of Constantius, convinced Vetranio to rule Illyricum, which he did for 9 months protecting this buffer area. He surrendered to Constantius and retired. Constantius continued chasing Magnentius, with the final defeat at Lugdunum (Lyons, France) in 353.

While battling Magnentius Constantius had raised his cousin Constantius Gallus to rule from Antioch in his absense. After Magnentius' defeat, Gallus was executed by Constantius, due to his harsh rule. A year later he raised his cousin Julian as Caesar to take command of the "barbarian" incursions in the western empire, as circumstances necessitated his return to the east to fight the Sasanians. Julian's popularity was such that he was proclaimed Augustus by the troops in 360. Constantius refused to accept this and died in November of 361 while on his way to suppress the uprising. On his deathbed he proclaimed Julian as his successor.

Flavius Julius Constans, born ca.323. Constans was only 10 when proclaimed Caesar by his father on Christmas of 333, and was placed as ruler of Italy in 335. He was elevated to Augustus after the death of Constantine in 337. In the resulting separation of the empire Constans received Italy, Africa and the Balkans for his rule. In 339 he surrendered Thrace and Constantinople to Constantius.

Constans was baptised in 337, and was firmly orthodox (Catholic).

When his oldest brother Constantine II invaded Italy in 340, he was killed by troops under the control of Constans. This left Constans with control of the entire western half of the empire. He spent much of his time protecting the borders against incursions by Germanic tribes, and won a decisive victory over the Franks in 341. Constans was the last legitimate emperor to visit Britain, in 343 to battle the Picts and Scots.

In 350 the general Magnentius staged a revolt against Constans with the support of the troops. Seeing no hope of victory Constans fled, but was captured and killed in southern Gaul in January of 350.