The childhood of Augustine is known only from what he chose to reveal in the highly selective memoirs that form part of his Confessions.
He depicted himself as a rather ordinary child.
From his description in his "growing pale with envy" (Confessions 1, 7) when he saw a sibling feeding at the breast of his mother, it would seem he was the eldest of the offspring of his parents, Patricius and Monica.
In his childhood Augustine would have had contact with Donatism, a heresy that later as a church leader and Christian author he combatted vigourously.
It is known from his writings that Augustine had cousins who were Donatists. They were sons and daughters of a brother or sister of Monica.
The brother of Augustine was Navigius. He was with Augustine at Ostia when their mother died, but not at that stage of mid-life a baptised Christian.
Augustine did not give the name of his sister, although paradoxically she was more a part of his story than was Navigius.
(Without any historical foundation, the name Perpetua has often been assigned her for the sake of literary convenience).
When later in life she was a widow and Augustine was Bishop of Hippo, his sister conducted a monastery for women there, apparently on his behalf.
The letter that is called the Rule of Augustine was in fact written to that community in a crisis of leadership caused by her death.