Daughter Swap did this for a while too, and they may still be. I haven't had a membership there is six or eight months. They had been careful to use the 'step' language for a long time and when they started, the stepdads and daughters wouldn't even be in the same room for sex let alone any contact. Back a couple of years ago, things started to change and there was the occasional 'accidental' contact but they did go all in with a few scenes. There are some descriptions in this thread. Those may give you some inspiration:
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