Di, my wife and I were invited to a Christmas party at he sisters house. Shelly and Tony had been together for four years and at times she could be a complete bitch, a right stuck up cow always superior and putting any one down with a flippant remark

Half way through the evening I happened to walk past the front room where all the girls were sat drinking and gossiping. I was some what surprised to over here my wife praising my sexual appetite,
“fuck Mike is such a pain he would fuck 24 / 7 given the chance” I heard all the girl laugh,
Shelly then said “if Tony can get it up twice a month im fucking lucky”
the rest of the girls went on to moan and praise the other halves, with various comment on what they would like their men to be better at.

I moved in to the kitchen and resumed a conversation with the lads. As with all bloke talk it turned to sex and we were laughing and joking about various aspect the subject when someone said about all women loving it up the arse,

Tony then went into a phase of how much he thought anal was disgusting and any woman that did it was lower than a whore.
It was a that exact time Shelly decided to enter the kitchen and heard him and in true style she said “what the fuck would you know what a woman would like perhaps some women like acting the whore” 
with that Tony shut up and as shelly walked out she gave me a sly wink,
now this was totally out of her character to be nice to me. Later in the evening as every one was getting drunk people were dancing in the front room.
with my wife fairly pissed and asleep up stairs, Shelly moved over to me and said “come on brother-law show me a good time and dance with me.
As we danced she deliberately started rubbing her groin against my cock and the inevitable happened my cock began to get hard.

Shelly leaned close to my ear and whispered mmm that feels so good,
she was a right tease and thrust he groin harder against my cock “ Tony is still here” I said.
she just laughed and told me what a tit he was, as It was dark she lowered her hand and slowly traced the out line of my raging hard cock. 
If what my sister said is true I could do with some of this she whispered and squeezed my cock hard.
Stop fucking about Shell! you would run a mile if I tried to fuck you,
well we will see and with that she stopped dancing and started to tidy up.

As the party was all but over I decided to make my way to bed.
Tony was passed out on the sofa and the last guests had just left.
I walked passed the kitchen and Shelly was at the sink cleaning dishes.

I thought its now or never, I walked up behind Shelly took a good hand full of hair twisted her head around a kissed her full on the mouth,
she tried to push me off but it was no use I was to strong.

As I broke the kiss she said, “what the fuck did you do that for”
I backed off and said “ because I can you prick teasing bitch.”
I turned to walk out and she said “wait” I then knew I could do as pleased, I walked over grabbed her by the arm and bent her over the kitchen table.
Wait, wait was all she could say but it was to late. I kicked her legs apart pulled her dress up over her arse and ripped her thong straight off,

This time she was saying “ no mike please no not here,” I released my hard thick cock and then thrust forward and entered her tight cunt,
although quite dry she was rapidly getting wetter,
No, no, no, followed by a long sigh mmmmmmm. I started to fuck her with long slow movements,
“fuck” shelly moaned as I pulled and pushed my hard cock into her wet juicy cunt and with each thrust she pushed her hips back faster and faster.
I reached around and grabbed her tits they were still under the top of her dress I moved my hands back to her hips and thrust full into her.
Shelly was moaning and groaning quite loud and I told her to keep it down but as I bottomed out in her cunt she squealed so I slapped her on the arse quite hard.
her reply shocked me “ I’m sorry sir” was her strange reply.

Could this hard nose sister in law be a bit submissive I thought in for a penny in for a pound,
get on your knees you dirty slut was my first command, 
with out a second thought she spun around and dropped to her knees.
Well what the fuck are you waiting for I said and the dirty bitch stuck out her tongue and licked every inch of my cock. I started to slap her face with my hard cock open wide i said and grabbing a good handful of hair I rammed my cock straight down her throat,

I was making her gag but she was loving it. I face fucked her hard for about ten minutes.
Get up and get into your dirty whoring position Shelly. I barked.
Shelly stood, rucked up her dress and bent over the table again.
Once again I entered her doggie style and started to hammer her pussy. Yes, yes, yesssss
Shelly screamed fuck me mike fuck your dirty sister in law come on you bastard do me harder, harder.
I carried on fucking her for a few moments then I pulled out and rubbed my cock over her tight arse hole,
No, No, not there, I again slapped her arse don’t fucking no me you whore, 
Slap, Slap,I Slap her arse hard.
Sorry sir I’m sorry, please not my arse I’ve never done that before.
Good looks like I’m going to show Tonys’ wife how much a dirty whore you really are,

I spat on her ring and slowly eased a finger into her tight hole, please mike I will do anything just don’t fuck my arse.
To late Shelly and I eased the tip of my cock into her virgin arse, as my sister in laws arse ease tightly around my cock, I pulled back on her hair, pulling her hair tight she arched her back as I fucked her arse.

Slowly she got used to the invasion in her once virgin arse, ever so slowly she started fucking me back,
my god she breathed I never thought it would be this nice, obviously her slight pain was now overwhelming pleasure, 

Shelly moan and moved her arse to quicken up the fucking taking place in her arse, mmm yes baby this is soooooo good, Mike do it, fuck my dirty whore arse, 
I kept fucking her faster and faster, I pulled out with a loud plop and rammed my cock straight up her flooded cunt then back into her arse, 
cunt few thrusts, arse few thrusts until Shelly was begging just my arse please just fuck my arse Mike
so we built up a nice hard motion. Just then shelly let out a loud scream and flooded come all over my balls and down her legs,
as the pace increased Shelly begged for me to come.
As I asked her where she wanted it she again surprised me by saying “ in me sir plant your strong seed in my belly” so I pulled out of her slippery arse and thrust back into her cunt.

After three hard prods I unleashed my come deed inside her. I lay on top of her for a few minutes then slowly pulled my cock out and wiped it on her dress.

I moved over and sat on a kitchen chair, Shelly rose pushed her dress down and bent down to pick up her torn knickers, they were from a set you bastard she laughed.

She then tossed them into the bin, as we sat talking she said that she had always fancied me and that the reason she is so hard nosed was to drive me away, so that her true feelings wont come out.

What do we do from here she asked, well you don’t want to hurt your baby sister and Tony does not need to lose his wife, 
Here are my rules. You will become my mistress; around the family you will act the same hard nose bitch that you are.
When ever I call you privately you will call me sir, you will always be ready to fuck me when and where I want, and to add a final bit of fun.
I will direct you in how to treat Tony.

The only choice is take it or leave it. Shelly stood walked over to me and kissed me with a passion,
She then lent over my lap pulled her dress up over her arse and said I agree sir.