Multiple men, same name, NT.
Cephas
1Cor.3:22 Whether Paul, or Apollos, or Cephas, or the world, or life, or death, or things present, or things to come; all are yours;
1Cor.9:5 Have we not power to lead about a sister, a wife, as well as other apostles, and [as] the brethren of the Lord, and Cephas?
1Cor.15:5 And that he was seen of Cephas, then of the twelve:
Gal.2:9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we [should go] unto the heathen, and they unto the circumcision.
Luke doesn't know anyone named Cephas, but calls Paul's Cephas of Galatians 2:9, by the name Peter, in Acts 15:7... while Act's James calls Luke's Peter by the name Simeon, in Acts 15:14.
Simeon
13:1 at Antioch ... Simeon that was called Niger...
15:14 Simeon hath declared how God at the first did visit the Gentiles...
2 Peter 1:1 Simeon Peter, a servant and an apostle of Jesus Christ, to them that have obtained like precious faith with us through the righteousness of God and our Saviour Jesus Christ:
Simon
1 Peter 1:1 Peter [the] apostle [of] Jesus Christ, [to the] chosen pilgrim Diaspora, [in] Pontus, Galatia, Cappadocia, Asia, and Bithynia,
8:9 But there was a certain man, called Simon, which beforetime in the same city used sorcery, and bewitched the people of Samaria, giving out that himself was some great one:
9:43 And it came to pass, that he tarried many days in Joppa with one Simon a tanner.
13:55 Is not this the carpenter's son? is not his mother called Mary? and his brethren, James, and Joses, and Simon, and Judas?
27:32 And as they came out, they found a man of Cyrene, Simon by name: him they compelled to bear his cross.
13:26 Jesus answered, He it is, to whom I shall give a sop, when I have dipped [it]. And when he had dipped the sop, he gave [it] to Judas Iscariot, [the son] of Simon.
James
two are the Apostles from Galilee...
15:7 After that, he was seen of James; then of all the apostles.
19 But other of the apostles saw I none, save James the Lord's brother.
13:55 Is not this the carpenter's Son? is not His mother called Mary? and His brethren, James, and Joses, and Simon, and Judas?
15:13 And after they had held their peace, James answered, saying, Men [and] brethren, hearken unto me: 14 Simeon hath declared how God at the first...
John
two are the Apostle and the Baptizer...
4:6 And Annas the high priest, and Caiaphas, and John, and Alexander, and as many as were of the kindred of the high priest, were gathered together at Jerusalem.
12:25 And Barnabas and Saul returned from Jerusalem, when they had fulfilled [their] ministry, and took with them John, whose surname was Mark.
So... who are these men named James, Cephas, and John...
Galatians 2:9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we [should go] unto the heathen, and they unto the circumcision.
...if Cephas was in Antioch when Paul went to Jerusalem to complain about the circumcision that came to Antioch from James, to talk with Peter in Acts 15:7... if Peter was already in Jerusalem?