A brother and sister story

I think it was from around ten years ago. It was collected over 5 or 6 parts. Each part has the siblings going a bit farther starting until in the end they have full blown sex. One particular part had the sister introducing her brother to her friends and all of them going out together.

Don't know if you're still around or if you ever found it, but the story is Ashley by ShiggyMoto. One of the first stories I remember reading and really liking on Lit.