Most of this I do not believe. I see nothing wrong with a Sister and Brother having Sex with each other, living as husband and wife and having kids.

In fiction I like the Sister to be a little older or twins, and for the female to be more or less in charge.

When you grow up togeather you see each others bodys unless you live in a very strict house. There are times when you become Teens that you are left alone for periods of time, the oldest watching the youngest.

As hormones kick in Attraction can be natural and there is somthing called natural progression. 1st base, 2nd base, 3rd base Home. With Incest its often stright to home.

Of course this is better when it is close aged, 1 to 3 years. Mostly with Siblings you will find Greater tenderness and love. Mostly because they care about each other.

Like any relationship it sometimes wears its self out. Some people fall in deep love and live as Husband and Wife, and have family and grow old and happy togeather.

Our Society says that Incest is wrong, that the Females are always the victims. Unless its a 300 pound mother sitting on her son.

That it always has violence and substance abuse.

In reality Not So Much, but those people keep quiet about it and do not admit or talk about it. So any survey is skewed.

The natural break time seems to be going away to college or into the service.

Of course being found out or PG or Religlious Confession of some kind is the greatest fear.

Isolation and Incest, is what starts Tribes, Races and Nations, so its been going on a long long time.

The anti-sex values of Religions have claimed it as a Taboo and Secular Law backs that up.

I do not evan consider Sex between Cousins, Halfs, Steps, and Adopts as Incest.