boy has 3-4 sisters at least 1 set are twins, they are all aliens or geneticaly altered, they get mind powers when they all have sex. Author had alot of stories that were sort of the same, I think one was called "redneck summer" but he was gonna change the title.
Any ideas?
Might this be the My Girls stories by Unknown1000u2? There are three stories in the series.https://storiesonline.net/a/unknown1000u2
Sounds like a Sir Winston story which are no longer on SOL. You can find a bunch of his stories archived at http://www.asstr.org/files/Authors/Apache/My Favorites/Web/Sir Winston/
