The Parselmouth Promise

HPDM. Voldemort's influence lingers after his death in the form of Parseltongue passed on to the children of everyone with a Dark Mark—or, in Harry's case, someone who once hosted a Horcrux. As Harry struggles to be a good single father to his son, James, he inevitably runs up against Draco Malfoy, who's not only a Parselmouth now but has a son who is, like Harry's son.