'King's' in the Bible

Now when he had gone, the king's servants came, and saw that the doors of the summer-house were locked; and they said, It may be that he is in his summer-house for a private purpose.

Then he said to Zebah and Zalmunna, Where are the men whom you put to death at Tabor? And they gave answer, As you are, so were they; every one of them was like a king's son.