We Did Bad.

I come from a very twisted upbringing. Prior to the days of internet, my twin sister and I shared our first porn together. It was of our parents with our aunt and uncle in a group setting. It was very graphic showing everything that you can imagine. Including cum shots, creampies, blow job's, and lots of them banging each other.
We still shared a room together, but with separate beds, but we were both developing. My sister had seen me hard countless times and more recently we had began mutually masturbating. She had also watched me cum. She was also very sexual, and would let me watch her play with herself while I wanked myself.
We had only just woken up to our parents leaving to go Xmas shopping for us, then began snooping through stuff we shouldn't have. Now, we were both in shock of this collection of family porn. We were also very excited by seeing our mothers pussy full of our uncles cock then cum, and the same with our aunt and our fathers cum. They practically did everything with each other and we saw it all. I was rock hard. There was no hiding it in my pj's.
My sister saw then pointed telling me I was hard from looking at them. I admitted that I was, and asked if she was turned on at all. She said she couldn't believe what they have done with each other and to have kept the evidence. They all act like siblings but they secretly banging.
I believe that moment changed everything for us two. We hadn't been touching each other up until that point. She would finger herself, while I jerked off. I'm sure it's a fairly common thing for kids to do.
We call it playing mommy's and daddy's once we began to do stuff with each other.
It started that day. We knew we had hours alone to play with ourselves, or each other.
We chose the latter.
I pulled my pants down and began stroking myself, then asked if she wanted to play with each other instead of just ourselves. My sister was pointing to a photo of my father balls deep in our aunts pussy and asked, like this? I said yes.
She asked what we should do, and I said we should take our clothes off first. She layed back on the bed and said, you get on top. So I did, and steered my cock towards her open pussy as I was doing so. My sister didn't have an intact hymen as she'd been fingering herself for a while. So I had only rubbed it up against her a few times and I noticed that the tip of my cock was going inside her. We were both moving a little, and panting. I noticed her juices were lubricating my shaft and I was going deeper. I asked how it felt, and she responded with good, so I kept going. Our little movements became larger as I was getting deeper, and we we basically fucking by then. I know the sounds my sister makes just before orgasm, and she wasn't making them from her fingers, it was my cock. This thought pushed me over the edge, and I started cumming inside her. As this was my first orgasm that wasn't from my hand, it was very intense for me. I came quite hard and deeply inside her. She waited until I had emptied my balls into he vagina and had stopped moving and said I should have taken it out before I came, so she can't get pregnant. I said that brother's can't get their sisters pregnant because they're to close genetically, and nature doesn't allow it. Just then I could feel my cock getting soft, and my cum started to leak out of her, straight onto our parents bed! I went with the urge to pull out, then heaps of cum poured out of her. I yelled at her to stop, and she said she was trying to stop it from cumming out, but couldn't. Now we had evidence to hide. We had to wash the bed spread and make up a story of how something was accidentally spilled on the bed for our parents.
I just couldn't believe what we had done, and knew we would be repeating it many times. I always came inside her, but she thankfully never fell pregnant. Soon she was taking the pill, so it became safe. We we fucking frequently from around 13 to 17 and agreed to stop before our eighteenth birthday. My best mate had caught us fucking one day, and we had a 3 way with him to keep him quiet. We both came inside her.
They ended up married with 3 kids. We no longer talk which I really regret.
I will admit that we seemed like the perfect match sexually. It felt like being twins made our genitalia fit like we we made for each other and we were addicted to making each other cum.
I still miss the sex as much as I miss her.
We tried to reconcile in our early 30s and ended up fucking several times over many hours behind our partners backs. All contact stopped after that. I think she confessed to him afterwards.
I wonder how many other siblings have taken this path?