She was the daughter of the Roman emperor Constantius Chlorus and his wife Flavia Maximiana Theodora, and younger half-sister of Constantine the Great.
[4] She had two sisters, Anastasia and Eutropia, and three brothers, Julius Constantius, Flavius Dalmatius and Hannibalianus.
[5] Constantius already had a son, Constantine I, from his previous relationship with Helena, making him Constantia’s half-brother.
In 313, the emperor Constantine gave her in marriage to his co-emperor Licinius, on occasion of their meeting in Mediolanum.
In the following years, Constantia lived at her brother's court, receiving honours (her title was nobilissima femina).