Note: This story was dynamically reformatted for online reading convenience.
 
 It was late on a Thursday night and my parents were going over to some
friends for a meal.  I had to stay at home to baby sit my 16 year old
sister.  Mom was one of those people who got very pissed very easily and
she normally gets very horny after drinking (so I found out seeing her with
my dad from previous nights they have been out).

   When it was time, I told my sis to go to bed coz she had school in the
morning. My sister was a very good-looking girl and is very mature for her
age, she has always had a boyfriend.  My sis and me are great friends and
we go to places together all the time.  After she had gone to bed I waited
for a while, then I had a good look around my parent's room to see what I
could find.  I was just about to give up coz I thought I had checked
everywhere but then I thought about the top of the dresser.  So I pulled
out the drawer, it was just Moms underwear.  I must have pulled the drawer
out too far and it fell out.  I picked it up and was going to put it back
when I noticed there was a video sellotaped to the back of it.  The thought
of finding a hidden video in your parent's room is quite a turn on with
different feelings.

   I grabbed the video and ran downstairs.  I shoved it in to the machine
and started watching it.  It was a video of Mom and Dad in a foursome with
the people that they are seeing tonight.  I must have had the volume on to
loud but I turned around and my sister was standing there only with her bra
on.  She had one finger in her mouth sucking it.

   I quickly turned off the television and the video and looked at her in
complete shock.  She asked in a calm voice "Can you put it back on?" I was
still in shock and said "y yy ye yes sure." So I turned it back on and sat
back down.  My sister came to sit down next to me and rested her head on my
shoulder and put her hand on my chest and slowly moving it down towards my
cock.  I had a ragging hard on and then her hand slipped through my pants
and I felt this soft hand stroking the length of my cock she took her head
off my shoulder and looked deep in to my eyes.  I could sense that she was
being very serious.  She turned around and looked at the TV.  Mom was
bouncing on top her best friend having full blown sex with the guy
squeezing her tits, and she was loving every minute of it.  While in the
background we could see dad pumping the other lady doggy style over the
couch, she had a very large pair of tits.  My sister turned around and
grabbed my hand and started stroking my hand over her pussy.  I heard her
groan, she was loving it.  The next thing I knew my sis was taking my
trousers off.  It seemed so weird, letting my sister see my cock.  As soon
as she got sight of it she looked at me and smiled as if she was teasing me
and slowly put my fully erect cock in to her mouth.  I still hadn't said a
word all night.  While she was sucking me off she kept looking in to my
eyes she wouldn't take them off me.  I slowly lifted my other hand and
started to undo her bra, she started to smile.  I slowly pulled it down and
started playing with her nipples, she was as turned on as I was.  She laid
down on the floor and opened her legs as wide as she could.  I knelt up
picked up both of her legs and pulled her towards me and then with a sudden
push I thrust my self in to her.

   After about five minutes she sat up and pushed me to the floor so I was
laying on my back and she again mounted her self on top of me.  I looked up
and it felt so strange seeing my sister being such a turn on.  When we
finished we both got dressed and cuddled up together and started to watch
the video.  Watching your parents doing strange things with other people
like mom sitting on dad and giving the other bloke a blowjob was a real
turn on.  We both started to feel horny again.  I slid my hand down my
sisters pants and she naturally spread her legs and started to get excited
again.  Then she slid her hand down my pants and we just masturbated each
other.  The whole night we must have said about 4 words each.

   The next morning I had got up too late to see my sister.  She had
already gone to school.  I walked down stairs and my Mom gave me the
strangest look I have ever had.  She walked out of the kitchen and went to
the living room and asked what this video was doing in the machine.  I was
sooo embarrassed, I didn't know what to say, so I didn't say anything.  My
mother asked me again "Did it turn you on?" I replied "what?" "Did the
video turn you on?" "Yes totally." I said.

   She grabbed my hand and pulled me upstairs as if she was raging mad. 
She took me in to my bedroom and pushed me hard on to my bed.  "Stay there"
She said, and to my amazement she started to strip.  "My god!  What are you
doing?" I asked she said "Shut up and watch!" When she was totally naked
she walked over to me and started to undress me.  She slid my trousers and
pants down to my ankles and took my cock into her hand and started to play
with it.  The next thing I knew she had got on to the bed and laid on top
of me.  With a quick thrust she forced my cock into her cunt.  She was so
rough and it was such a turn on I sat up and started to kiss her deeply and
to my surprise she was kissing me back.

   I said to her "We haven't go any protection." "Shut up jut tell me when
you are about to come" she said.  She must have been riding me for about
twenty minutes "aaaaahhhhh Mumm - get off I aaaammm..." She quickly stood
up and grabbed hold of my cock and started to suck I exploded into her
mouth.  She quickly mounted again to get the second helping I put my hands
on her hips and sat up helping her with the excitement.  I grabbed hold of
her tits and started playing very vigorously with them.  She was at her
peak of her orgasm she was screaming so loud.  When we had finished she
just told me not to tell anyone, then she asked me if I enjoyed it?  I
replied I have wanted to do that for such a long time you would not believe
it.  A few hours later she said to me, while I was down in the kitchen, to
go to the shops and get a few packets of condoms; we'll need them for this
week.

   My mother was 47, slim for a person of her age and had the nicest pairs
of tits.  She had an inplant when she was younger.  And she was a very good
looker all my friends said she would be a complete babe if she were a bit
younger.

   Later in the day my dad came back from work and my mother was feeling as
horny as hell.  Dad sat down on the sofa and Mom came running in with a
lovely black lace bra and a very short skirt on.  She hadn't put any pants
on all day.  She jumped on Dad and took his pants off and just like that
they were having full blown sex lying on the sofa.  I walked down stairs,
into the living room and saw mom and dad at it.  My Dad looked all
embarrassed.  He told me to go back up stairs.  Then Mom said "Stop.  Come
over here." I walked over to my parents and looked at Dad who was totally
enjoying him self with Mom bouncing on top of him.  Mom undid my pants and
started sliding her hand up and down my cock.  Then she stuck into her
mouth.  Then Mom said it was my turn, as she laid me down on the floor she
didn't let go of my cock once.  She got dad to lay down next to me.  She
mounted me and then kept swapping between me and Dad.

   Then the door opened and there was my sister.  She stood there in total
shock with mom hitting her orgasm and all three of us laying down naked and
completely turned on.  It took a while for my sister to register.  But she
quickly took of her clothes and started to wank Dad off.  After a few
minutes she mounted him.  As he grabbed hold of her maturing tits she gave
off a small scream.  Mom and sis were alternating between me and dad.  We
just laid back and enjoyed the ride, both of them.

   In the last couple of months, my sister and I, while we have been in the
house, have been acting as if we were a couple.  With me and my mom it's
like - whenever she feels horny she lets me know about it.

   Only a few months ago we had two more people in the house.  Mom and I
had a son, and Dad and my sister had a daughter.  It is really weird in the
house now coz just about every night we have a session in the living room.

   If we aren't having sex we are fondling each other.  I enjoyed it best
with Mom because she didn't mind what we did or where we did it.  The best
experience that I can remember was when one of my friends came over.  We
were having supper and mom was sitting next to me.  I started fingering
her, hiding my hand under the table.  She didn't move my hand and half way
through the meal she gave out this big groan.  She stood up grabbed hold of
my ear and pulled me up stairs and took me into her room then started to
toss me off.  She pulled down her pants and I thrust my hard cock in to her
cunt as I pushed up against the wall.  She stopped me for a moment and said
"We can't be too long because they will be wondering where we are..."

   Later on in the day after my friend had gone, I was up in my room.  My
sister came in with a camcorder, she was as horny as fuck.  "Lets make a
film with just us two." She had hired a nurse's costume.  She stripped
slowly and grabbed me, pulled me over and took my clothes off.  I still
hadn't got a stiffy yet.  My sister hadn't seen a soft cock before.  She
didn't realise how much they grew with excitement.  She started the
camcorder rolling then walked over to me and started to play with me. 
Placed my dick in between her tits she started rubbing them together.  She
then put me to the floor and started tossing me off, I had a raging stiffy
now.  She sat on top of me and inserted me into herself.  She slowly
started moving up and down.

   You don't believe how much of a turn on it is to see, feel and interact
with your sister in a sexual way.  Mom walked in and watched us for a
while. She got totally turned on and then walked over and started licking
my cock while my sister was bouncing on top of me.