Genres date from the first written forms in ancient times where Plato and Aristotle classified the written text into three forms (poetry, drama and prose). These three forms became more complex over time and developed into our current system of having a myriad of styles, forms, etcetera as the need arose.
A lot of aspiring authors want to know what genre they write in. Google 'novel genre' and you'll soon find the many websites that 'help' determine which genre you have. Personally, however, I believe it's not the task of the author to determine the genre of your novel; the reader does. The writer who believed his novel to be in the historical fiction department may suddenly find his book in all the romance bookshelves.
So genres aren't solid, not over time nor through your audience. Then what does a writer do at all concerning genres? Nothing. That's right, nothing at all until you're getting published. Then you just ask your proofreaders for help in categorizing your novel so you send your novel to the right publishers. Beyond that the writer's concern is writing.