Maybe the legend of the kings is bound up in the Old Testament.

Book of Psalms, Psalm 72:
10 The kings of Tarshish and of the isles shall bring presents: the kings of Sheba and Seba shall offer gifts.

11 Yea, all kings shall fall down before him: all nations shall serve him.

12 For he shall deliver the needy when he crieth; the poor also, and him that hath no helper.

This is sometimes the Psalm set for Epiphany Sunday (commemorating the arrival of the wise men)

It is generally thought that the idea of three wise men/kings is based not on the number being mentioned in the New Testament (it isn't) but on the fact that there are 3 named gifts.