In his serialized attempt to convince us that Jesus took his burial shroud with him following his resurrection and gave it to John the Apostle who was the servant of the priest mentioned in a fragment of text from St. Jerome that quotes the Gospel of the Hebrews, Stephen Jones explains that Jesus and John were first cousins and that the Apostle John was also a priest.
I know that, didn’t I? Did I? If so, I didn’t know why. Very ingenious analysis by Stephen:
Mark and Mathew evidently record the three prominent women disciples standing by the Cross after Mary, the mother of Jesus, had been taken by the Apostle John (Jn 19:26-27), her nephew (see below), to his home. That the remaining three women mentioned are the same group in each account is shown by Mark listing "Mary Magdalene, Mary the mother of James, and Salome" as the women who went to the tomb in the early morning after the sabbath to anoint Jesus’ body (Mk 16:1).
That means that Jesus and Apostle John were first cousins:
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Mary was also a "kinswoman" of Elisabeth, the mother of John the Baptist (Lk 1:36 YLT). The Greek word for "kinswoman," sungenis, is simply the female of sungenes "a kinsman" (Mk 6:4; Lk 1:58; 2:44; 14:12; 21:16; Jn 18:26; Ac 10:24) including "of tribal kinship" (Rom 9:3; 16:7,11,21). Elizabeth was one of the "daughters of Aaron" (Lk 1:5), that is, she was of priestly descent and the daughter of a priest. Therefore Mary, and Salome her sister, were descended from David (Lk 1:32) and so were of the tribe of Judah (Mt 1:1-6; Lk 3:30-31) and also they were descended from Aaron, and so were of the tribe of Levi (Ex 6:16-20). There is no contradiction in this, as while a priest had to be a descendent of Aaron, he was not required to take a wife from the descendants of Aaron but the only requirement was that she was an Israelite virgin (Lev 21:1,7,14). The conditions of Jesus’ descent from David (Mt 1:1; Rom 1:3; 2Tim 2:8; Rev 22:16) are satisfied if at least one of Mary’s parents were of Davidic decent.
Therefore, for the Apostle John, the son of Salome, to be a priest, it was only necessary that his father, Zebedee (Mt 4:21; 10:2; Mk 1:19; 3:17; 10:35; Lk 5:10), was of Aaronic descent and therefore was a priest. And that would have been so if Mary (and Salome’s) father, Heli (Lk 3:23), i.e. "Eli" – a priestly name (1Sam 1:9; 2:11; 14:3), was a descendant of Aaron and therefore a priest. And that would have been the case, if the father of Elisabeth, who was Mary’s and Salome’s kinswoman, was a brother of Zebedee, John’s father. Further Biblical confirmation that John was a priest is found in Jn 20:4-8, where John reached the empty tomb first but did not enter it until after Peter went in and confirmed that Jesus’ body was not there. It was forbidden for a priest to enter a tomb where he might make contact with a dead body and so become "unclean" (Lev 21:1-3).