9) You need to confuse everybody. This will make sure that nobody can be really certain WHAT they believe, because it is all so non-sensical to begin with. And when you don't spell it out exactly (or even if you do) you know how those funny humans will all magically just get along, right!
In this case, we'll try to be real thorough here:
The Gentle Goddess Dietima and The Great God Lardicus are Divine Brother and Sister. However, they are also Husband and Wife. And The Great God Lardicus is the child of Himself and The Gentle Goddess Dietima. As is Dietima. They love each other, but argue and even fight regularly for a variety of reasons that we won't go into here because we want people to make up their own reasons, which they can then fight over.
We don't even have to explain how any of this is possible because they are Gods and can do whatever they want. We don't want to specify who was born first or the details of their immaculate self-conceptions, because that might give one side the upper hand in any arguments. Remember Rule Number 5: Keep it ambiguous.
The Gentle Goddess Dietima and The Great God Lardicus may or may not have other children, parents, siblings or acquaintances. We can add them in later if we want or need to, and then the old-timers (historians, scholars, etc.) can fight the new converts (who are always the most passionate about things) about whether they should "really" be in the pantheon or not, since they weren't there in the beginning. We'll probably just say we found some ancient scrolls that nobody is allowed to examine that mentioned them when we want to add in any new characters. That'll be fun!
Okay, let me give it a try:
The loving creator YHWH has a son named Jesus, who is also Himself. In essence, the son is also the father, yet they are one and the same. Furthermore, the mother of Jesus is the son of YHWH. Therefore the creator is both the father and son of the mother of Him. In this way, YHWH/Jesus gets to be born by, impregnate, and conceive Mary.
What's that you say? Someone already made that one up? Son of a bitch!
Christianity: spiritual incest at its best.