You don't have to write a sequel to this specifically because you have to write HAPPY Matthew/Mary/Lavinia. God damn it what is the point of an OT3 that solves a love triangle if there is no happy ending! The only sadness should maybe be some believable guilt at living in such a way given how they were raised, but I like to imagine they'll be in Bloomsbury so like VSW can soothe that and stuff.