The dynamic of Ren's family reminds me of Otonashi Kyoko's family in Maison Ikkou. It's probably a coincidence, but the mangaka's earliest published work was in the mid-90s. She's probably old enough that it could have been an influence.
Also, file under "things that make you go, 'huh'": She apparently also has a work titled "Incest Heaven." 🤨
