The Creator defines humanity

And God said, Let vs make man in our Image, after our likenesse: and let them haue dominion ouer the fish of the sea, and ouer the foule of the aire, and ouer the cattell, and ouer all the earth, and ouer euery creeping thing that creepeth vpon the earth. So God created man in his owne Image, in the Image of God created hee him; male and female created hee them. And God blessed them, and God said vnto them, Be fruitfull, and multiply, and replenish the earth, and subdue it, and haue dominion ouer the fish of the sea, and ouer the foule of the aire, and ouer euery liuing thing that mooueth vpon the earth. 
 - Genesis 1:26-28 KJV-1611

The first prophecy defines marriage

The first man (and first prophet) defines marriage:

And Adam said, This is now bone of my bones, and flesh of my flesh: she shalbe called woman, because shee was taken out of man. Therefore shall a man leaue his father and his mother, and shall cleaue vnto his wife: and they shalbe one flesh. And they were both naked, the man & his wife, and were not ashamed. 
 - Genesis 2:23-25 KJV-1611