Complex sentence: Isidore was probably born in Cartagena, Spain to Severianus and Theodora, members of an influential family who were instrumental in the political-religious maneuverering that converted the Visigothic kings from Arianism to Catholicism.
Split into simpler sentences: Isidore was probably born in Cartagena, Spain to Severianus and Theodora. His parents were members of an influential family who were instrumental in the political-religious maneuverering that converted the Visigothic kings from Arianism to Catholicism.