During a vacation me, my gf and her little sister had to spend a night in the same room 1 big bed and a small one for her. during the night i woke up to the sound of the little sister masturbating. after she was done i softly told her that it was very naughty and i wouldn't be able to sleep for the night. she came on over and gave me a blowjob, swallowing my cum all down. my gf lying next to me was obliviously sleeping on. I hope we'll have more fun like this in the future. Thoughts on turning her sister into a fucktoy for both of our sexual frustrations is crossing my mind, I love my gf loads and wouldn't ever want to leave her.