Mark and Jennifer were very close, most people put it down to the special bond that all twins have.

Mark was the eldest, by just nine minutes, he was a typical twenty-one-year-old man about town, a regular at the gym, and even had his multi gym to work out at home when he didn't have much time on his hands, although other times he would sometimes just prefer it to go to the gym.

Jennifer was quite the opposite, she was very beautiful, with a slender body, long blonde hair and piercing blue eyes, like Mark she also had a good job, but she wasn't confident at all. She thought she was too plain and nothing much to look at, she certainly attracted the attention of young men, but almost seemed to not even notice.

They say that opposites attract and Mark and Jennifer proved that point.

One fateful day changed everything for the adoring twins. Their parents had found them a large apartment to share, coming from a wealthy family, buying it for them was not an issue, it had three bedrooms, one of which now contained Mark's multi gym, two reception rooms, and a decent-sized kitchen.

Being young professionals, Mark being a junior teaching assistant, and Jennifer a veterinary nurse, the siblings were able to equip the apartment themselves.

On the day in question, Mark was working out at his multi gym, he had started in his training gear, but it was a boiling hot day and he soon took off his tee shirt and shorts, leaving him in just boxers and socks, his sister was at work and even when she was at home, she very rarely ventured into his gym room anyway.

He had been training for about half an hour, with his usual brand of classical music playing, so he didn't hear the front door open and close.

He also didn't hear the clicking noise of Jennifer's high heels on the tiled floor between the door and the living room.

In fact, by the time he did hear her, she was in his gym room and watching him on the bench press, staring at his six-pack stomach and toned muscles in awe as he lifted the huge weights.

When he finally realized she was there he was so shocked that he nearly dropped the bar and weights on his chest, it was only through his strength that he avoided serious injury and was able to lift the bar back up to its resting place above him.

Jumping up and grabbing his discarded shorts and tee shirt he shouted in surprise, "What are you doing in here?"

The timid answer was, "I was only watching."

There was a definite change of atmosphere in the room as the twins strangely eyed each other, not saying anything, just looking.

Mark's cock started twitching, he knew he was the confident one, but his sister was like the original girl next door who everyone would fantasize about, he knew she was an object of desire for several men, now including him, it had suddenly snuck up on him without him realizing.

Jennifer returned her brother's hungered look, while also smiling devilishly, giving way to erotic feelings that had lain dormant inside her, now flooding to the surface at the sight of her stud twin brother and the increasing size of his obvious hard-on.

They could have stood there several hours for all they knew, such was the timelessness of the situation, more likely it was only minutes or maybe even mere seconds, how long it took didn't matter, but what happened next definitely did.

Quite out of character, Jennifer strode forward, put one hand down her brother's boxers, grabbing his eight-inch piece of meat, while simultaneously kissing him, both their mouths opening, teeth colliding and tongues exploring each other's mouths.

Immediately Mark started to rip her clothes off her, with her red two-piece suit pulled off her, swiftly followed by her cream blouse, before her black lace bra and knickers were torn apart and thrown aside.

Mark sat on the bench where shortly before, he had been working out, but this time he pulled his practically naked sister in front of him and started to tease her pussy with his tongue, before sinking it right into her, making her moan out loud and throw her head back in sheer ecstasy.

Once her sweet nectar was in his mouth he lay down on the bench so she could stand over him and lower her pussy to his mouth, while also taking his rock-hard, throbbing member in her mouth and sucking him for all she was worth, before another orgasm washed over her, making her shudder from head to toe.

Before the pleasure became too much, Mark bodily lifted her off and bent her over onto the bench, he moved behind her, sticking two fingers up her soaking wet vagina, causing her another bone-shuddering release.

As he took more control, he started to rub her precious, virginal opening with the head of his cock as pre cum oozing out of it.

She said, "This is risky Mark, I'm not on any contraceptive."

He replied, "I'm not worried if you aren't?"

With those words, she grabbed his cock in her hand and guided it into her smooth pussy, allowing him to take her virginity, knowing what the result could be, but not caring.

Mark had been with other girls before, but nothing felt as satisfying as the incest he was enjoying with Jennifer. He fucked her as hard as he possibly could, the endurance of his weight training now forgotten and replaced with a sheer will to make his sister want his cock more and more.

While he slapped his cock deep into her, Jennifer pushed back against him, making grunting and groaning sounds as her brother pounded her mercilessly, making her cum all over his cock, her vaginal walls clinging onto him desperately, before his release also came, making his hot, sticky sperm fill her pussy until it was dripping out of her, both drawing deep breaths and smiling at the same time.

Mark stayed inside her until he had no more cum for her, at which point his softened cock flopped out of her.

Jennifer stood up straight, his sperm drooling down the inside of her legs, both smiling, twins understanding that everything had now changed for them, but knowing it was all they had wanted to do for longer than they could remember.

Mark said, "What happens now?"

Jennifer simply replied, "Yours is the bedroom with the double bed, whenever you're ready."