So I had a random idea, and it can be a small group rp or one person playing multiple characters or just one on one. The plot is the mother and father were hunters. (We can figure out the exact type of hunter when we discuss it in more detail if we want to be specific.) When the daughter/daughters (I could be talked into a femboy or futa if you want.) Are young the mother and father are gravely wounded, fighting an incubus. the mother was the medic and she used the last of her life to infuse the incubus life force into her husband. As she fades away he swears he will never love another all his love will go to the daughter/s so they grow up happy.
Fast forward up to you depending on how we bank the story and the age you want your character. The father quit being a hunter and was using all the money from retiring and being a stay-at-home dad, for the girls. However, what no one knew was the incubus life force saved his life but it also was a parasite and it was eating away at him every day, recently it hit the point where he couldn't hide it anymore.