Only the Gospel of Matthew has the story of the Magi (2:1-12) and it does not even say how many there were! In the Middle Ages, these astrologers began to be called “kings.”
At various times, numbers other than three have been suggested. Christian tradition probably settled on that number because the Magi brought three gifts. The Venerable Bede described Melchior as old, Gaspar as young, and Baltasar as black. Those names and details are not in the Scriptures, though they can remind us that Jesus, the light to the nations (Isaiah 49:6), came to save all people everywhere.