“For no man ever yet hated his own flesh; but nourisheth and cherisheth it, even as the Lord the church: For we are members of his body, of his flesh, and of his bones. For this cause shall a man leave his father and mother, and shall be joined unto his wife, and they two shall be one flesh. This is a great mystery: but I speak concerning Christ and the church.” (See Ephesians 5)
When the Apostle Paul spoke of this he was inspired by the Holy Spirit. It harkened back to God's thoughts in the Garden of Eden. The relationship has been tied by God between a man and a woman, but secured through the marriage of that man and that woman to represent the relationship between Christ and His Church. No matter what the political thoughts and practices of any culture drifts toward, it will never change the intent of God.