***
The Egg had been formed decades ago. It had sat patiently inside the ovary of the girl for twenty years waiting to make the marathon journey down a fallopian tube. Specifically that of the girl the Egg came from, Emily Cann. The previous egg had passed without her conceiving; this Egg was next. As the Egg entered the girl's fallopian tube, it began massive hormone changes inside Emily to increase her libido and lubrication, as well as help guide a sperm to the incoming Egg.
***
A WEEK LATER
Emily Cann arrived home from tennis practice, sweaty and tired. Hours outside had left her normally light skin with a slight rosy hue. "I hope that tans later", Emily thought as she caught her reflection in the hallway mirror of her parents home. Her normally dark red hair now a rosy strawberry blonde, having been bleached instead of darkened by the summer sun.
She was a beauty by any standard. All the boys on her tennis team thought so. Including her brother Eric Cann. The tight pants and tennis tops revealed a gorgeous figure. None of them could help but notice the curve of her hips or her perky breasts. Eric least of all. He followed closely behind his sister through the door of their shared family home, discarding his racquet and gear.
Placing his hands on her hips he turned her and kissed her sweaty lips softly. They both quickly glanced around the living room but it was empty as usual.
Emily too was enthralled by her siblings body. She had first noticed his generous manhood during practice as long sweats became tighter shorts.
Neither sibling could resist the illicit temptation of exploring each others bodies. And so they begin doing that. First with quiet touches and fingerings. Then on to more enthusiastic licking and sucking, before full on fucking.
They had developed a routine weeks ago to avoid the suspicion of their parents, which wasn't hard due to their parents rarely being home. First Emily would look around upstairs and if the coast was clear, start the water in the bathroom as if for a shower. She took this time to update the period tracking app on her phone. At the same time Eric would walk though the first floor to see if anyone was home. He was supposed to use this time to relieve himself if he was too excited about the couple's planned activities.
This was the deal Emily and Eric had made, he would be careful about when he would cum, making sure to pull out in time, and she would track her period to avoid dangerous times. They had agreed there could be no accidents that would lead to their parents finding out about their activities. The siblings loved each other too much to risk being separated.
Neither had been doing a good job of being diligent, however. Eric never rubbed one out when he knew his sister was willing and waiting right upstairs, and Emily often got so distracted with the thoughts of Erics cock while she preened herself that updating her tracker slipped her mind entirely. The girl hadn't noticed her cycle was off by almost two weeks now. When the notification popped up telling her that the cycle has just begun, though her period ended weeks ago, she thought nothing of it.
***
At the same moment Emily was receiving the notification, her brothers body completed production of a sperm cell. It was one of millions produced that week, but this one would be the next to travel down his penis. The Sperm floated in Eric's balls amongst millions like it, all eagerly waiting to make the journey.
Emily's tracker continued to deceive her. She believed an egg was about to be released from her ovary, but in reality the Egg had already dropped in to the final section of the girl's fallopian tube.
***
Eric walked up the stairs past the bathroom to his sister's room next door. It's there that she was waiting. The couple began to softly kiss and touch each other. Eric's hands gently stroking his sisters gorgeous red hair and soft neckline. He unzipped the top of her tennis shirt and it fell around her sports bra.
