Chapter 1

Lisa Jenkins held her breasts as she stood in front of the mirror. They were large and tender... She realised for certain now that she was definitely pregnant... What had started off as a joke to play on her twin brother Joe had back fired rather badly, and he'd ended up making her pregnant.

To explain, Lisa and Joe had been having sex with each other since the age of sixteen. After their sixteenth birthday party, which had been a disaster, due to their parents inability to understand their age group, they had consoled each other in Lisa's bedroom.

They had both had too much to drink and were angry because their parents had treated them still as small children. "God, we're old enough to have sex and marry now. Are they ever going to let us grow up!" Lisa had complained.

Joe had held her in his arms and her skirt had risen up exposing that she was wearing a small black pair of bikini pants. It was the first time he had ever seen her in anything other than school regulation underwear. Her sumptuous tits were heaving out the top of her blouse and he could see she had a matching black bra. Her long, sexy legs were tanned and soft and rose to a pinnacle hidden by the short skirt. Frustrated she had started to undress for bed and had noticed the bulge in Joe's trousers. Laughing she had touched for his erect penis and was surprised by the size of it. "Is my sexy underwear causing this?" she had giggled. Joe had become totally erect and she had unzipped his trousers and masturbated him until he ejaculated. She had been absolutely fascinated by the squirting white fertiliser he had emitted from his body. He then kissed her breasts and made her orgasm by licking her through her knickers. And now two years later they thought they had got it off to a fine art.

Lisa's favourite method of having sex was to get Joe to lie back on the bed with his knees bent and feet on the floor. To make Joe erect she would slowly strip off and dance around the room in her most provocative underwear which she would slowly divest herself of. Joe would gently masturbate his growing erection and when she could see he was ready she would remove her knickers and stand between his parted legs with her back to him... positioning the tip of his penis between her vaginal lips she would drop down on him, allowing his erection to penetrate her totally in one action... She always orgasmed at this and would then slowly 'post' up and down savouring the exquisite size of his manhood.

Joe had to remember the 'safe word' when he was about to come so she could lift her body off his penis before he impregnated her. They had tried various contraceptives but for one reason or another they had not suited them. The Pill had made Lisa fat and because of Lisa's fetish for taking Joe's penis in one lunge they had noticed that one or two of the condoms had split. The danger was they could never be sure the latex rubber was intact before Joe's ejaculation. Occasionally they resorted to anal sex but this required a huge amount of pre-preparation of Lisa's backside. Whilst she loved Joe oiling her big bum and pushing his fingers inside her rectum to properly lubricate it, the spontaneity wasn't there. They now practised the 'withdrawal method' of contraception which meant they could have sex without preparation and although they hadn't discussed it they knew it added a little bit of spice to the act.

Lisa and Joe always loved to play tricks on each other and so it was this that caused her to misjudge the event that led to her pregnancy. Joe had issued the 'safe word' but instead of lifting her body off his penis immediately so that he could ejaculate safely she had stayed for just one more second so she could use her tight vaginal muscles to squeeze his large erection one more time. She had expected him to delay his ejaculation in panic, but she did not understand a man's urges when triggered. Joe had pulsed a single swathe of his semen into her unprotected cervix before she lifted off to allow him to pump 5 or 6 more strokes safely onto his stomach.

Two months and two missed periods later the results were plain to see. Her breasts had swollen from her normal 34 C to massive 34E and her tummy was beginning to swell. She held them in both hands marvelling at their size and how they were stretching her white skin so much that she could see blue veins.

Another set of hands covered hers and she removed hers to let her twin brother take their weight. "Sorry " said Joe "but I did say the safe word..."

"I know" consoled Lisa " I never realised the risk."

That one shot of semen they had found out since contained the vast majority of Joe's sperm. A medical reference book they had found warned them that Mother Nature had a way of catching out those that casually practised withdrawal. They had read that the first shot of semen often contains far more sperm than the subsequent shots which were mainly seminal fluid. To make matters worse Lisa had asked Joe to quickly lick out his unwanted liquid and in doing so she had orgasmed and unwittingly sucked his sperm into her cervix. As luck would have it her body had released a ripe egg that day and Joe's sperm, well, you know the rest...