Crossing Roles

It was never meant to happen, yet a year on we're now lovers.
My sister Helena returned home from uni for a few weeks last year and within days I walked in on her, as she masturbated with a dildo.
Instead of telling me to get out, as she had all our young lives, my sister invited me in and told me to lock her door.
Sat on the end of her bed, I watched as she fucked herself and played with her clit. It all looked beautiful to me and I was soon incredibly turned on.
Then letting go of the dildo, she asked me to fuck her. It just seemed natural for me to grip the seven inch sex toy and begin sliding into my sisters soaking wet pussy.
At the same time, she reached under my skirt, slid my knickers to one side and massaged my pussy and clit.
It wasn't long before we both had strong powerful orgasms, with my sister thanking me by kissing me fill on the mouth.
The following day, with our parents at work, she lead me upstairs to my room and undressed us both.
Lay naked with her, we kissed, caressed and slowly played with one anothers sex.
It was so beautiful, so perfect that when she moved us around, I didn't hesitate once to lick along her pussy slit, part her labia with my tongue and gently suck on her gorgeous clit.
We gave each other oral sex lay in a sixty nine for over half an hour.
My sister took me to multiple orgasms with her mouth and fingers, probing my pussy and arse with her digits. And I followed suit by finger fucking her love holes too.
It was a magical loving and very sensual experience for us both. And once we'd settled down after our sex, we promised each other we'd continue to explore one anothers sexual pleasures.
And so we have. Each time she returns home, or I visit her at her uni digs, we have such wonderful times together. We've bought dildos and a strap to fuck each other, plus my sister has a 'Sometime' boyfriend who we share when I visit her.
He's a nice guy, but knows we're using him for his large cock. He doesn't care and if I was him, I wouldn't either.
I also have a girlfriend who I visit as part of my farm, agricultural studies. She's very masculine and loves to dominate me sexually. But that's another confession.
One thing I do know, is my sister and I have pledged to always enjoy each other and given how amazingly close we are, I think we'll always be lovers.