The whole reason for Melchizedek was to show mankind, who are saved, that the eternal priesthood was without sin and Spiritual.The bible says Melchizedek was without mother and father. Children who are born again to eternal life, are born by God without mother and father. Melchizedek is symbolic of that Priesthood. Jesus was told by God, He was a priest forever in the order of Melchizedek. Since Jesus is our high Priest, we are Priests forever in the order of Melchizedek. Since Jesus is Eternal God, He has complete authority over Melchizedek. The Bible doesn't tell us about Melchizedek's beginning , but it tells us where we, as the saved of God will spend eternity. God created everything out of nothing, so where does that put Melchizedek? Could be he was a theophany.