Audrey was scared. Her twin sister Jamie had just arrived back from college, and Audrey struggled to keep her dick in her pants. Not only did Audrey accidentally call her sister hot, but she also ended up half-accidentally seeing her sister naked as Jamie came out of the shower (Audrey was horny and wanted to see her sister in a towel, but didn't expect Jamie to be fully naked). Audrey eventually went to Jamie's room to apologize, but Jamie kissed her! Audrey then had her virginity claimed by her sister, but right after both of them finished, the twins were caught by their mother.
Mom was standing there in the doorway, looking casually at her naked girls. Audrey's dick was still in Jamie's pussy, and cum was dripping down onto the bed. Jamie had a faster reaction than Audrey. Jamie quickly unmounted herself from Audrey's dick, and pulled the bedsheets over both of their bodies.
All Audrey could do was lay there in shock. Mom wasn't panicked, which was good, but that was even more weird! Audrey just fucked her sister! Any normal person would be panicking right now, just like Audrey was!
"Uh, Mom. We were... Me and Jamie were..." Audrey started to ramble, but she didn't know what to say. How could she justify what they did?
"Audrey, Jamie, it's alright. You two are fine," Mom said.
Out of everything Mom could have said, that stunned Audrey the most. Audrey felt like a broken machine, like a yes or no question answered with a million maybes. What was going on in her mother's head?
"I suppose there's an explanation that I owe you girls," Mom said. "Come on, sit up." Mom sat down on the bed with the two sisters, and began to pull them into an awkward hug.
Jamie was giving her mother a half hug, as she was trying to keep the sheet above her breasts. Mom could clearly tell how uncomfortable the twins were.
"Hey, we're all family here right, there's nothing to be embarrassed about. Let me see those bodies," Mom said.
Jamie slowly dropped the sheet, showing her luscious breasts. God, Audrey had loved sucking them. But Audrey wasn't as brave as her sister, and she kept her half of the sheet covering her body.
"Oh please, how about this," Mom said. She easily reached under her shirt and pulled off her top and bra. She then followed with her own pants and underwear. Mom was buck naked, but she seemed perfectly comfortable like that.
"There, we're all naked together. Can you two please come here?" she said.
Mom grabbed both Jamie and Audrey's waists, and fully dragged them out of the sheets. The three women were all completely naked, with their bodies pressed up against one another.
"Okay Mom..." Jamie started to say. "What exactly did you want to tell us?"
"I never really explained it, but there's an important reason the two of you never met your father," Mom started to say. "A long time ago, your great-great-great grandmother, whose name was Edith, insulted a fairy in her youth."
"Wait sorry, a fairy?" Audrey asked.
"The story is a bit of a myth, I don't know how real some of the details are, but it'll lead into the important bits. Anyway, that fairy was said to have cursed Edith, making it so that she could only reproduce with her own spawn. This meant that Edith was infertile, but her dream was to be a mother someday. Eventually, Edith found another fairy, and although the fairy couldn't lift the curse, she could give a blessing to counteract the effects, turning Edith into a futanari."
"Since Edith had a penis and vagina for herself," Mom continued, "she was able to collect her own sperm, and after a few attempts, impregnate herself. After having a few children, Edith discovered that she couldn't have male children, and could only have daughters, and some of those daughters ended up being futanari. She also discovered that the curse was passed down to her children. However, there was a way that the children could reproduce. With each other."
"Wait," Jamie started. "So our dad is...?"
"Your dad is your great aunt-Helen. I asked her to impregnate me, so I could have the two of you," Mom said.
"Shouldn't that mean a lot of genetic problems and stuff?" Jamie asked.
"Well, I think my two little girls are too pretty for that to be a real concern," Mom said. Audrey felt a faint blush appear on her cheeks. "Our family would have noticed by now if that was an issue."
"Okay. So why didn't these... urges happen before?" Audrey asked. "I mean, I always knew Jamie was attractive, but I never was really attracted to her before."
"That's a bit of a special trait with twins," Mom said. "Usually, people from our family don't have any special attraction towards each other, but twins are different. Whenever twins happen, there is always at least one futanari, and the twins have an incredibly strong attraction towards each other, especially when they are identical. The attraction begins when the girls are about 20, give or take a couple years."
"Does it... last forever?" Audrey said. Jamie shot Audrey a look. Audrey didn't exactly know what it meant, but she clarified, "It's just pretty distracting. Every time I look at Jamie, I get really horny, and while I love you Jamie, it's going to be hard for the two of us to be around each other." As Audrey, said that, she could feel her cock growing again on her leg.
"Well..." Mom continued. "It ends if Jamie gets pregnant with your child Audrey."