Alypius was born in the middle of the fourth century in Tagaste, Africa, to parents who were influential citizens of that city. He studied law in Rome, but first met Augustine while at school in Carthage. Augustine praised Alypius, whom he called "the brother of my heart", for his honesty, sincerity and sense of justice. Like Augustine, Alypius was at one time a Manichean. The two friends were both converted to the Catholic faith and were baptized together by Saint Ambrose in 387. Alypius was a member of Augustine's first monastery in Tagaste. When Augustine was ordained a priest in Hippo, and founded a community in that city, Alypius joined him there, and was subsequently ordained bishop of Tagaste around 384. He once traveled to the East, where he met the great biblical scholar Saint Jerome. He took part in the African Councils of the Church during his time as bishop, and was chosen along with Possidius and Augustine to represent the Catholic bishops at the famous meeting with the Donatists in Carthage in 411. He took part in the Council of Milevi (Numidia) in 416 and composed a written report on this Council for Pope Innocent. Alypius travelled to Italy several times as part of his opposition to the Pelagian heresy. He carried Augustine's writings with him in order to present them to Pope Boniface. It is believed that he was present at the death of Augustine in 430. Alypius died shortly thereafter, probably later in the same year.
Possidius, the first biographer of Augustine, was born in northern Africa, and became a member of Augustine's first monastic community in Hippo, along with Saint Alypius. He was named Bishop of Calama (Numidia), where he faced opposition from the Donatists. Possidius narrowly escaped death on one occasion when Donatist extremists set fire to a house where he was visiting . Twice he went to Italy to defend the rights of the African Church. He was present at the Councils in Carthage in 403 and 407, and was chosen along with Alypius and Augustine to represent the Catholic Bishops at the famous meeting with the Donatists in Carthage in 411. He also took part in the Councils of Malevi (416) and Carthage (419) which treated of the Pelagian heresy. When Calama was conquered by Vandal invaders in 429, Possidius took refuge with Augustine inside the walls of Hippo and was with Augustine at the latter's death in 430. Possidius returned to Calama, but in 437 was exiled by King Hunmeric, who suppressed Christianity and forced Arianism on the territories that he conquered. During this time of exile, Possidius completed his famous book, The Life of Augustine. He died in exile around the year 437.
The Order has celebrated the feasts of Alypius and Possidius since 1671. Clement X confirmed devotion to them on August 19, 1672. The memory of these two saints is closely tied, both as monks and bishops, to that of Saint Augustine. They are, in fact, the two greatest representatives of his monastic legacy. However, it is not for this reason alone that history remembers them. They were dedicated Christians, religious and shepherds of the Church in their own right.