itch.io

In the game, do shift-O to bring up console, then type the following to disable incest:
set_special(False)

Type exit to get back to the game

I would have liked if the game starts out as Mrs. Smith providing a home for the protagonist and the girls, hiding the fact that she is their mother. This fact can be hinted at, and eventually exposed half way through the game. Might add more intrigue to the plot. (obviously the revelation would not occur for the non-taboo version). But overall a really outstanding game, congrats.

Perhaps they'll join you a few days later? (hint hint)

Is it possible to get full harem without anybody pregnant?

I think a lot of people did. You can get almost everyone.