Should it be incorporated into a tale?
Incest. Calls to mind scenes of brother raping sister. Of father molesting daughter. Of mother seduced by son. Mostly, in today’s society, it is firmly in the public consciousness as a Bad Thing, so you say it and people do lean in the direction of rape and molestation, drugging, slavery, torture. Even in the V C Andrews book my sister likes so much (no, I haven’t read it and I know it was a series and so am uncertain which title to reference, sorry) where the incest is treated far more consensually and even slightly more romantically … it’s in the face of abuse and isolation. It’s not so bad, next to everything else going on in the characters’ lives – or so I gather from listening to her go on and on about it. Even if I’m mistaken, it’s a good point and one someone has probably published. QED.Again, we're dealing with two different things, both of which should be written about...
1) abuse/assault and
2) consensual experimentation/sex.
Two very different things, both of which do exist, and both of which need to be addressed in fiction. It is because there is such a difference between those two things that I refer to the second as consanguineous sex or consanguinamory. Young people need to know that the first one is not OK, and the second one is not necessarily a problem.