A Lesson in Biology
Copyright© 2026 by Lubrican
Chapter 8
Coming of Age Sex Story: Chapter 8 - She wanted to be a cheerleader but her grades were too low. Summer school might solve that problem. But she needed a tutor to make sure. Her mom got a name from the school and he was hired. When they got to the biology tutoring, she wanted to understand the reproductive system. He was happy to teach her about it.
Caution: This Coming of Age Sex Story contains strong sexual content, including mt/ft mt/Fa Mult Teenagers Consensual Heterosexual Fiction Incest Mother Son Brother Sister Harem Interracial Black Male White Female First Lactation Masturbation Oral Sex Petting Pregnancy Voyeurism
“What do we do, now?” asked Keesha.
They stood, looking at each other. The girls looked at where Marcus’s erection pushed the torn fabric away from his body. His big, black balls could be seen where nothing covered them.
“You’ve really seen him like this?” asked Tasha.
“Only once, really. Do you guys get to see him like this?”
“Every day,” piped Keesha. When Tasha looked at her, the younger girl said, “Just tell her. Marcus said to. Even if she tells, nobody will believe her.”
Robin looked at Tasha.
“You grabbed him just like I grabbed him.”
“I told you, I study biology with them, too,” Marcus repeated.
“Do you go all the way?”
“Marcus!” Tasha moaned.
Marcus ignored her and looked into Robin’s eyes.
“Yes,” he said.
“Not fair!” Robin said, immediately.
“You and I can’t do that because of the rule,” he said.
“Well, they don’t have a rule. Wait.” She looked at Keesha. “Do you mean you do it with him, too?”
Keesha just smiled.
“Why aren’t you dead? How could he get that thing in you without killing you?”
“I stretched,” said the youngest girl there. “He went slow and I stretched and he got almost all of it in me. I love it. I wish I could do it right now.”
“Damn, Keesha, just tell her everything we do!” moaned Tasha.
“I will if she wants to know,” said Keesha, firmly. “I’m her friend and she’s my friend and we both love Marcus. She won’t hurt us.”
“That’s true,” said Robin. “I would never do anything that hurt Marcus.”
“Tell us what you’ve done,” said Tasha.
Robin closed her eyes.
“We were studying biology and he got stiff. I noticed and he asked if I wanted to see it. I did, so he showed it to me and I played with it and he squirted on my boobs.” She smiled. “I liked that a lot. It was warm and slippery, like lotion.”
“That’s it?” asked Tasha, sounding confused.
“He put his hand in my panties and put his finger in my cunny and he made me cum. I loved that part, too.”
“But he didn’t fuck you?”
“You know better than to use that word, Tash,” said Marcus.
“You make love to us. You can’t make love to a white girl. It just isn’t right. You can fuck her, but you can’t make love with her.”
“You’re making him go soft,” Keesha complained.
“Soft?” said Molly, her voice slurred. “It’s no good to me soft.”
“Good grief,” groaned Tasha. “Her, too?”
“We’ve never actually touched each other. Well, we kissed, but it was only once. My relationship to her is ... different. It’s not anything like what I do at home.”
Molly’s head rolled back and forth.
“If I suck it will it get hard?” she murmured. “Why am I in the ocean?”
The teens had moved to Robin’s room. The new revelations changed the dynamics of the group. In a sense, they were Norming. A fragile trust had developed and now everyone in the group shared a similar goal. In the long term, that goal was to maintain their freedom to continue loving each other. In the short term, the goal was to make Marcus ejaculate.
It was Keesha’s idea.
“Let’s take him somewhere and we can all help jerk him off. It will be like we’re all sisters.”
“Don’t I get a say in this?” said Marcus.
“No,” said Tasha. “You’re the one causing all of this. You use that irresistible cock on everybody. You make us addicted to it. You’re like pot. You play with it and it gets you high. Then you put it in us and turn it into heroin. We have to have it and you’re going to do the same thing to Robin. I know you are. And we make it soft at home. Will there be enough for everybody?”
“If you’re that worried, why don’t I get everybody off right now? I’ll take care of you three and then I’ll go take care of Molly and Mom.”
“You mean ... your mother, too?” Robin sounded like she’d seen a UFO.
“Truth and honesty,” he said. “I love making all my sisters happy and I love making both moms happy.”
“You just fucking want to breed somebody,” snorted Tasha.
Marcus looked at her.
“If you don’t fix that potty mouth of yours, there won’t be enough left for you. That could last for a couple of months.”
“Geesh, Marcus. You don’t have to go nuclear on me.” Tasha’s voice pouted.
“Then quit acting like a bitch. You’re not sexy when you do that.”
“I’m sorry,” she said. She looked at Robin. “I’m sorry for the stuff I said to you, too.”
Robin waved a hand like she was pushing air away from her.
“Sisters have spats sometimes. Until you came along I didn’t have any sisters, but I’ve heard other sisters talking.”
“Good,” said Marcus. “Now kiss and make up.”
“You want me to kiss ... her.” Tasha glanced sideways at Robin.
“If you’re genuinely sorry, and you genuinely accept her as a sister, you’ll do it. I’ve seen you kiss Keesha before.”
“That’s only when we’re really turned on,” said Keesha. “We’re not lesbians, or anything.”
“I’ve never kissed a girl, except for my mother,” said Robin. She sounded unsure.
“If you two kiss and make up, I’ll suck your clits until you cum.”
“What about me?” Keesha complained.
“To punish them for fighting, I’ll make them watch as you and I make love.”
“Now you’re talking,” said Keesha, excitedly.
She looked at the other two girls.
“Get to kissing! I’m horny and I want Marcus’s love pole in my pussy.”
The plan morphed a bit when Robin and Tasha pressed their lips together. Robin was surprised at the warmth and softness of Tasha’s lips. Tasha was surprised that a white girl would make the kiss longer than was probably required. When they parted, they looked in each other’s eyes.
“Can we be friends?” Robin asked.
“I think we can,” Tasha replied.
“I changed my mind,” said Marcus. “Rather than treat anybody or punish anybody I want to see all three of you act as a group with one accord.”
“And do what?” asked Keesha. She was unhappy because she might not get to have Marcus in her until they got home.
“I want all three of you to suck it, and when I cum, I want to cum on all three of you at the same time.”
“So, you want to dominate us and make us service you, like we’re sluts,” said Tasha.
“No. I want all three of you to work together to bring me off. And yes, by cumming on you I’m claiming you, but that is only because I want to claim all of you at the same time so you really do feel like this is one family.”
If we were still comparing this group with the usual definition of group dynamics, what this group entered now was the Performing phase. The girls acted as a cohesive unit, working efficiently toward the common goal of getting Marcus to spurt.
Obviously, his two blood sisters had more experience with his oversize organ, so they put Robin between them and all three knelt in front of Marcus. They were all naked by this time, the rest of the bikini parts having been left lying scattered around the edge of the pool. Their mothers looked comfortable and were sleeping. The night was warm, so they were left alone. Marcus had a raging boner by the time he stepped up to the three girls, on their knees, looking like they were ready to serve him.
But appearances can be very deceiving. Marcus was not, other than demanding they blow him to prove they were now a single unit, the one who was dominant in this situation. Rather it was Tasha who took charge. She demonstrated to Robin how to concentrate on the round knob at the end of Marcus’s penis, behind which was a convenient place to clamp one’s lips so she could suck without there being any leaks. In no time Marcus was making noises. Keesha then showed what to do with a smaller mouth, which meant she had to be more careful about her teeth. When Robin finally tried it, she felt no trace of revulsion at the idea of a man’s penis being in her mouth. This wasn’t “some man.” This was Marcus, and she loved everything about Marcus’s body.
The sequence went back and forth, from side to side, and since Robin was in the middle, she got to put her mouth on him between each of the other girls. That didn’t matter, since this was Robin’s first blow job and they wanted her to have as much fun as possible.
They began to taste him and Tasha told Robin what that meant.
“He’s getting close. He’s leaking a little in our mouths. Usually I like for him to shoot in my mouth because I like the taste so much.”
“I’m not that big a fan of getting it in my mouth,” said Keesha. “It tastes okay, but I’d rather have him shoot in my pussy.”
“But couldn’t that get you pregnant?” said Robin.
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