I'm sure you thought the answer was so obvious that it would be beneath contempt to say "Three". Actually, I'm pleased to be able to tell you that the answer is quite surprising.
In fact the Bible never mentions the presence of three (or any other number of) wise men at the manger when Jesus was born, even though you might think it does. Their names are just as absent as the manger and their quantity, even if you happen to think you know that one of them was called Melchior and the others were . . . well . . . can't quite think of them just at the moment.
You might attribute the idea of 'three wise men' to the mention of the three gifts of gold, frankincense, and myrrh, but as evidence goes that is a little thin. However many there were, according to Matthew the 'astrologers' went to see Jesus in a house not a stable:
“And when they came into the house, they saw the young child with Mary his mother, and fell down, and worshipped him”(Matt. 2:11)
Incidentally, Luke's gospel is the only other one to mention the birth of Jesus, and he neglects to mention either the star or the wise men who followed it. Mark and John have nothing to say on the matter of the birth at all.
So how old was Jesus when they found him? There is no mention of the 'twelfth night' of Christian tradition. In fact he could have been up to two years old because when the wise men failed to return to Herod to tell him about Jesus, Herod set out to kill all the children under the age of two. Presumably anyone could tell the difference between a new-born baby and a 2 year old?
So this is yet another case of the bible not actually saying the things that all Christians believe it to say.
What a surprise!
Not only that, but Matthew keeps telling us which prophecy was fulfilled by each part the story, ensuring that we, the ignorant readers, are perfectly clear about the purpose of the wandering stars and miraculous escapes from unrecorded historical massacres.
Without these hints we might not have found it so totally believable!