I was talking with some other writers and the subject of series came up. How do you create one? If you give your characters a HEA at the end of the story, what next? The secret for me in my short stories has been character development and relationship development. The pair always starts out unequal:
Colum is a monk captured by a Viking and enslaved
Luke pays Slader to kidnap him and use and abuse him
Straight Sam needs money so he plays a manhunt game with closeted Derek, gettin’ assfucked if he loses
Over successive stories, the power balance equalizes:
Colum learned to fight at his old monastery, and he fights to save his friend and assists the Vikings in battle against all taboos, when all is lost, earning their respect
Luke becomes more than a handful for Slader to master, intriguing him
Sam discovers his gayness with new buddies, freaking out “straight” Derek who can’t handle his own sexuality
By the end, you’re not at equality but you’ve got a more complicated relationship:
Colum is a free man, a warrior/lover to Viggo the Viking
Luke joins Slader’s kidnap “crew,” and the two of them use and abuse dudes together
Sam and Derek have a real gay relationship, though Derek is still squeamish about, say, sucking a dick.
Same with my stepbro stories, or any other series of books or stories I have planned. If you have a static power dynamic/relationship, then all you can do is repeat yourself.
I read something about sitcoms where a writer said the thing about scripting them is that nothing must ever change. No real lessons are “learned,” everyone is the same at the end as they were before the “complication” at the beginning of the episode. Same thing with action movies or books – Jack Reacher is always the guy he was at the beginning of the series. John McClain, same guy. Etc. The driver of the story is the humor in the sitcom, the comeuppance of the Fool. The action drives the action movie; the hero is a cipher and the interesting character is (in a good one) the bad guy (Vincent d’Onofrio in Daredevil on Netflix!).
I started my first novel series, with a HFN at the end. Marc and Jesse are just starting down the road with their potentially very kinky relationship. So there will be action/adventure/humor of the Nick and Nora type, sexin’ that weaves in their evolution, etc.
TL;DR if you establish a permanent power dynamic between two romance MCs at the end of a book, your only series options are to create a world (the ranch, the town, etc.) where you take secondary characters in the first book and give them their own HEAs in the rest of the series.
Thus Spaketh Bradasuthra.