Irenaeus says flatly that Peter and Paul established the church at Rome.
Do I really need to post the quote again?
No, but I am clearly not the only one who doesn't believe Irenaeus on this point and neither do honest Catholic scholars like Richard P. McBrien who writes in Lives of the Popes: The Pontiffs from St Peter to Benedict XVI:
"Although Catholic Tradition, beginning in the late second and third centuries, regards St. Peter as the first bishop of Rome, and therefore, as the first pope, there is no evidence that Peter was involved in the initial establishment of the Christian community in Rome (indeed what evidence there is would seem to point in the opposite direction) or that he served as Rome's first bishop . . . He often shared his position of prominence with James and John . . . However, there is no evidence that before his death Peter actually served the Church of Rome as its first bishop, even though the "fact" is usually taken for granted by a wide spectrum of Catholics and others." [Harper, S.F. 2005, pp 25,29]