Gaspar, Balthasar, and Melchior?
Grass is taller than the sky,
Only answer I don't know. Perhaps it has something to do with grass for the camels?
and rubies are taller than grass,
They brought huge 'treasures' to the birth of jesus.
All three gifts are ordinary offerings and gifts given to a king. Myrrh being commonly used as an anointing oil, frankincense as a perfume, and gold as a valuable. The three gifts had a spiritual meaning: gold as a symbol of kingship on earth, frankincense (an incense) as a symbol of deity, and myrrh (an embalming oil) as a symbol of death.
We are three kings, three brothers of many, known to mankind since time immemorial,
They are 3 brothers (of many more):
The tradition that there were three wise men arose from the fact that the Bible mentions three gifts, gold frankincense and myrrh according to Matthew 2:11. Howerver, the Bible doesn’t say how many wise men made the journey to see the baby Jesus. The unfounded idea that they were also kings came from the imagery of Isaiah 60:3.
Most men know all three of us, but some know fewer except perhaps by reputation,
It's a christian holiday, so they know who they are. Other people with other believes, only know them by reputation (heard of from others).
Together we can create something pure.