Flesh and blood did not reveal that same thing (and more) that was revealed to Paul, either, whom was as much a spokesman for God's truth as was Peter. Paul was not subordinate. He did not learn what he knew, at the feet of other Apostles.
Paul said that through Jesus Christ our Lord, he "received grace and apostleship," just as had the Twelve. Peter himself confirmed this (Galatians 2; 2 Peter 3).
Paul's says God's household, the Church, is "built on the foundation of the apostles, with Christ the chief cornerstone. Peter says that "commands are given by our Lord and Savior through the apostles."
Here's a question: are all believers apostles? Paul wrote, "God has placed in the church first of all apostles, second prophets, third teachers, then miracles, then gifts of healing, of helping, of guidance, and of different kinds of tongues," and then asks, "Are all Apostles? Are all prophets? Are all teachers? Do all work miracles?"
The answer is "No." There are diverse gifts given to diverse people, and "apostleship," while "first," was one gift, but not given to all.
The gift of the Spirit was and is given at the laying on of the apostles’ hands (Acts 8); it was and is likewise being transmitted to a new generation of successors by the laying on of hands: to Timothy (2 Timothy 1), Titus, those who were appointed by the Apostles (not self-appointed; not popularly elected, but appointed by the Apostles) to plant local churches and to teach and govern them with authority.
False prophecy also abounded. Paul says there are many "false apostles, deceitful workers, masquerading as apostles of Christ."
So, another question: how does one tell one from the other? Paul goes on, "I persevered in demonstrating among you the marks of a true apostle, including signs, wonders and miracles."
So we have these truths: that those who have the gift of apostleship are the foundation of the Church; that Christ gives commands through the apostles; that true apostles are accompanied by signs and miracles; that they appoint new apostles by the laying on of hands.
Paul had the commission of apostle to the Gentiles, Peter to the Jews. Peter also had the “keys,” a Biblical sign of office for an official who should rule in his Lord’s household until He returns. Because Peter loved the Lord more than the rest (John 21:15), he is given, more than the rest, a share the Good Shepherd's ministry of “feeding the lambs and the sheep,_ a shepherd of shepherds --- and, after he recovers from his stumble, he is appointed the ministry of “strengthening (or confirming) the brethren” (Luke 22:32).
It is Peter who confirms that Paul’s apostleship is correct (Galatians 2, and 2 Peter 3). This is true even though Paul on one key point has to correct Peter! Paul is not correcting Peter’s doctrine, --- Peter knew, directly via a vision from the Lord (Acts 10) that there was no distinction between eating “clean”: and “unclean” animals --- but Paul corrected Peter for his behavior, his waffling, his cowardice, for not acting in accord with what had been directly revealed to him by the Holy Spirit.
Thus we have the ministry of the Apostles, which continues to this day. Christ has not left us orphans.