im tired and sick of people like you that dont know shit of what you are talking about, because is the mom or sis doenst mean they cant add sex scene fast, that just stupid bad writing from devs that dont know how write plot at all, i can assure you there can be a lot of sex if only the plot was good and there is a lot of ways to get it, look icstor and other devs like Luxee that atleast have some skill when it comes to writing, go play parental love.
Incest doenst mean and will never mean slow building, thats just bad writing.