To be honest, I was thinking weather to reply or not, but entire talk about NTR in this game is, how to put it, an empty speculation. Dev wrote that he and his team did not plan it. I know that he left a possibility for inclusion if there is demand, but I wouldn't bet on it. First, introducing it in a game after two years of development is bad idea. This isn't soap opera where random elements like sudden introduction of character such as long dead uncle, long dead ex wife or twin separated at birth is good idea. Game gathered specific following, and introduction of very controversial theme is, like I said bad idea. Second, I don't think anybody seriously requested it. For all we know, it's few posts here, from people to lazy to look at tags...
In the very end, it's up to developers team. But, I don't think they will do something this risky and awkward. PS; notion to the mods and whomever else concerned, I didn't want to this to be abother NTR bashing post, this was a rant about pointless speculations.