"In The Roman Martyrology the Church seems to officially acknowledge Saint Peter's paternity: "St. Petronilla, Virgin [and Martyr], daughter of the blessed apostle Peter, who refused to marry the nobleman Flaccus. Given three days for consideration, she spent them in fasting and prayer. On the third day, having received Christ sacramentally, she gave up her spirit."
But the less official sources are not all so sure. Some place her death in the first century, where it would have to be if she were Peter's daughter, but others date it as late as the third century. Some, noting that her body was found in the catacomb of Flavian Domitilla, suggest that she was a member of the Roman senatorial family of the Flavii. The inscription on her tomb reads "Aure‘ Petronill‘ Fili‘ Dulcissim‘," possibly indicating relationship to an earlier branch of the Flavii, known as the Aurelii. She is not mentioned in fourth century calendars, but this absence may actually place her death in the first century, before the Church began to venerate the martyrs liturgically.1 A fourth century fresco in the cemetery of Domitilla depicts her about to be put to death.2 But there is some evidence that the Martyrology is accurate in naming Petronilla as St. Peter's daughter. Another painting, made around 356, presents Petronilla "receiving a deceased person (named Veneranda) into heaven."3 This strongly suggests that she was venerated as a saint before this time -- and it is interesting to see her performing the duties normally associated with Saint Peter (perhaps, filling in for her father?).
We know from the Synoptic Gospels and from patristic sources that St. Peter was married, so children are not beyond possibility. Clement of Alexandria related that Peter's wife died a martyr on the same day as Peter (i.e. not after an abnormally brief marriage), and that Peter had children who (in contrast to the daughters of Philip) apparently did not marry. A daughter of St. Peter is mentioned but not named in the apocryphal gnostic Acts of St. Peter. Obviously, the name 'Petronilla" could be a diminutive of "Peter.'"Continue HERE