What is meant by and they two made a league together 1king 5 v12?

Jewish answer: King Solomon and Hiram king of Tyre made a pact to work together in constructing material for the Holy Temple. That is the meaning of the verse in its context.

ANSWER:

God sent the two children of Israel into the world and ultimately they must be united as one in the eyes of God, and serve him. That is the work of the human, so when the Bible tells us about the brethren and the neighbour, that references are twoards these two, and not that physical person. See Genesis 25v23, "And the Lord said unto her, two nations are in thy womb, and two manner of people shall be seperated (because at that time the evil was present) from thy bowels and one (the good) shall be stronger than the other people (Evil); and the elder shall serve the younger. However, this will not be possible without a divine intervention.