I see your account has been suspended, but would like to comment in general.
Natural law predates any written law or any revealed law, and so it predates the Bible. It is not, however, to be confused with behavior of the early Homo Sapiens “in the wild”. Think of it as similar to the laws of physics, likewise predating science books yet by far not obvious to people without special education.
Marriage is a lifetime sexual union of a man and a woman oriented toward procreation and fidelity even if it fails at these ideals, — according to the natural law thus understood. Other forms of sexual activity may feel or even be product of natural instincts, but they are illicit per the natural law, just like jumping from high buildings may feel natural, but is contrary to the laws of gravity.
Good man-made laws approximate the natural law. Bad man-made law contradicts it. Laws in various jurisdictions that facilitate non-marital sexual behaviors of either hetero- or homosexual kinds are bad laws, regardless of the mechanisms by which they were made. For example, if 100% of the population votes to make a law creating homosexual unions, it is still bad law.
Come on now, you sound like my kids. I'm old, but not that old.