The One God
The first commandment is: Hear, O Israel, the Lord our God, the Lord is one.
Why do we have one God?
Our God is one because if there are two gods, this would mean that one of th two is greater than the other. This would also mean one of the two existed before the other and the one who existed before is greater - as such, the one who existed later will not be god.
Only one god will reign, should two gods exist. The second would not be god, because he must follow the one who leads.
God is omnipresent, there is no need for another.
In the Bible, we read that the one Lord cannot give His glory to another:
When the people of Israel worshipped idols (e.g. the golden calf) - God became angry at them.
When the Egyptians of old worshipped an entire pantheon of gods, God commanded Moses to lead His people of Egypt, that they may worship Him.
Likewise, people who worship idols, animals, plants and even other human beings are not right because they are not gods - they do not possess the power or the might to do everything and to be anywhere at any time.
Contrary to popular fiction, our Lord cannot procreate with a human being. We cannot accept, by all means, the marriage of the divine to the carnal because:
Humans can only procreate with humans. Anything else is not logical, acceptable nor biblical. This is very clear. We see this even in the animal kingdom. Never in the history of mankind, have we seen an elephant mating with a lion - but we certainly have seen the mating between a male elephant and a female elephant. If this is the case with animals, so it is for humans, let alone the one God.
In addition, we have witnessed some people, ordinary people, who were not married - like the great saint, Anthony, and the monastics and hermits. If a man like St Anthony was able to be celibate for God, what more can we say about the one God who created St Anthony?