“Among whom are ye also the called of Jesus Christ:”
Among whom, Paul is referring to “for obedience to the faith among all nations, for his name:” in verse 5 when he says “Among whom”. That is, among the Gentiles who had become obedient to the Christian faith in hearing and believing the gospel of Jesus Christ. Paul using the phrase “among all nations” proves that the church at Rome was made up partly at least, if not mainly, of Gentiles or pagans. This is also proven by the names of the persons whom Paul salutes in chapter 16.
Those whom Jesus Christ has called to be his followers. The word “called” denotes not merely an external invitation to privilege, but it also denotes the “internal” call which secures conformity to the will of him who calls.