I've been following ($$$ on Itch, and Sub on your Patreon!), your game since "Day 1" (sandbox RIP), release. I'm actually not sure if I could get into the MC being directly related to the twins at this point. Being related to thier Step Father is kinda solidified in my head (particularly after those dialogue's you mentioned). It would be jarring to try to change that perspective at this point. I'm similar in perspective with GF Nicole, having enjoyed every interaction with her to date, and only want to see her included in occasional scenes later, (particularly with Ava. Even in a Harem ending Nichole would remain #1 for me. I already like her too much). I only mention it because I'm all for corrupting the girls, while maintaining a compassionate/emotionally intimate relationship. I certainly want to see them exploring, and later, playing with eachother as well as the other characters, both with and without the MC directly involved. I've been looking forward to "seeing" if that can play out. (I also harbor a fantasy that in a potential future series of events you can humble their bitchy mom and dominate the hell out of her with the help/involvement of Kevin, Kayla, and Nichole. Ava, my satisfied sub, will of course, assist. lol).
Long preamble, but I'm curious if the "patch" you speak of, could optionally preserve the established "step" relationship while also allowing the Twins/Sisters to "get closer" (this potentially also includes Misa and Mei too).