Here we go:  Adam and Eve constituted the first marriage union between a man, a woman, and God.  They were instructed to subdue the Earth and be fruitful and multiply, but once they sinned enmity was brought between them and they were in disunion.  Regardless, God said, "what I have joined together let no man put asunder", and they went on to populate the Earth and subdue it as commanded.

Many other commands followed because Adam and Eve, as well as their descendants, were like uneducated infantile children who knew nothing beyond what God tried to teach them and what they experienced on their own apart from him.  His commands included prohibitions against sexual relations with anyone of the same sex and I will list some of them for you to look up on your own when your ready to allow Him into your heart to avail you to the Truth. His!!!

- Leviticus 18:22
- Leviticus 20:13
- 1 Corinthians 6:9-10
- Roman's 1:26-28

Peace be with you