Brother + Sister + Incest Stories

Zoe falls asleep in her brother's bed. He decides he needs to lose his virginity, and the universe has just given him a near naked girl delivered straight to his bed. What does it matter if it's his sister?

I'm sure my sister is no different to anybody else's. She's reasonably happy to wander about the house in her bra and knickers, I suppose she doesn't really see me as being male for I am two years younger than she is. On a couple of occasions I have even caught her walking from the bathroom to her room wearing just a large bath towel around her waist and a smaller one around her wet hair

From the Family Feud universe, a short story to see if there's interest in such a spinoff....

Marty tells his sister about a theory he has - the "Big Tits Theory" - while feeding her body-altering, mind-bending milkshakes.

I did read a book just like the book described here.

Lilith Ripinski is a 15-year-old loner, with an annoying 17-year-old brother named Samuel. One day, he pushes her just a little bit too far, and they enter into an intense, surreptitious sexual relationship. "The Book of Lilith" chronicles the development of their incestuous dynamic, their struggle to keep it secret, and the way Lilith's confidence grows as a result of feeling desired for the first time.