My sister's Friend

A few weeks ago my sister's friend (Let's call her Heather)(Now Heather is 20 years old, a cute little brunette about 5'4", 32D tits and a round ass) came over for a barbecue looking amazing in a figure hugging dress that showed off all her perfect curves, her shapely ass, her amazing tits , it being a barbecue people were drinking (I was teetotal as I had work in a few hours) I had popped upstairs to use the toilet BUT forgot to lock the door behind me, midflow her friend bursts through the door needing a pee also, but she doesn't leave she just watched me pee, so i shook the last from my cock zipped up my flies and turned to leave but she grabbed my hand and said "I watched you don't you wanna watch me" (Now it's safe to say I have a bit of a fetish watching girls pee)So I replied "Yeah" and listened to her piss cascade from her pussy, When she had finished she dried herself off with some tissue and on her way out the door she whispered "Maybe more next time I see you Cheeky" but I thought nothing of it really until I had to give her a lift home as she lives about 10 minutes from my work the entire journey she had her hand wrapped around my cock tugging occasionally she asked me to drop her off at the corner near her house because she didn't want her parents to see her just before she got out the car she said "Next time I'm over I wanna taste it" I said "You're more than willing to try it" So last night my sister had some friends over because she had just split up with her boyfriend, so they had been drinking to drown her sorrows or whatever I was just trying to sleep with all the noise that was going on anyway, I was just dosing off when I felt the covers raise and a hand pulling down my boxers I flick the light on to see Heather on her knees at the side of my bed she asked me to turn off the light so she could give me a blow job I was more than obliged, I was hard within seconds as she took my throbbing cock in her mouth whilst massaging my balls with her hand, I couldn't help but push her further down my shaft I heard her gag a few times she was sucking for a good ten minutes when I could feel myself ready to cum so I asked "Want me to tell you when I'm cumming" She said "No" but with my cock in her mouth it sounded more like "mo" I think she knew I was cumming as my balls tightened and my hips jerked as the thick sperm hit the back of her throat "mmmmmmmmmmmmmmmmm" she said, then she got up and said "Don't tell anyone about this" then went to the bathroom to I guess clean up a bit and that was that I waited for her to finish in the bathroom so I could clean myself up.