They are gods, not human beings. It may be weird to us but imagine every god is a being created by one god from nothing so it's basically their clones dating each other kind of thing.
Of course, if you still don't like it or are uncomfortable with how gods are doing something "incestuous" that humans do then just skip it cause the whole thing is incest haha..
In all polytheist mythology, gods are siblings and married to one another. Which doesn't matter because they aren't human, with DND, They all come from the same original source. So technical incest in terms of family tree, but nothing out of the ordinary regarding gods story.
And you should actually read it because it is really good.
why is this tagged as incest