A really useful blog is that of the Ubi Petrus blog, run by a former Catholic who is now Eastern Orthodoxy. A useful resource is the following page:
All Bishops Are Successors of Peter
This is important as it shows that early Christians did not believe that the Bishop of Rome was the singularly unique successor to the Apostle Peter.
All Bishops Are Successors of Peter
This is important as it shows that early Christians did not believe that the Bishop of Rome was the singularly unique successor to the Apostle Peter.