The end.

Kira, who was still pinning Lara's lips with hers, could feel her wife's body shudder under her touch. She pulled back, watching Lara's face as she tried to regain her composure. "Oh, honey," Lara said softly, brushing a strand of hair away from her forehead. "I'm sorry. I shouldn't have said that. It just felt so good... and Jack was soo..." She trailed off, unable to finish the thought.

Meanwhile, Jack was still buried deep inside his mother, his eyes wide with shock. He'd never heard her say anything like that before, and it left him feeling both confused and aroused. He watched as Kira stroked Lara's hair, trying to calm her down. "It's okay." she said reassuringly. "Maybe it is time for his to know." But Jack couldn't help but wonder what Lara had meant by that comment. And as he continued to keep her hips pressed tight to his tights, he felt a strange mix of emotions: desire, curiosity, and some small betrayal.

Lara, catching her breath, looked over at Jack, her eyes meeting his in the mirror. There was a vulnerability in her gaze that he'd never seen before. "Jack... I... I should not have said that, but..." Her voice trailed off, and she turned back to him, her hands reaching up to touch his face. "I love you, Jack. I've always loved you."

"Wait, mom, so you knew my father? I though I was adopted? And if you knew my father, are you my... biological mom?" Jack blurted out all of the questions he had in his head right on Lara. He couldn't help but feel a little stupid asking this question, considering their respectable phenotypes.

Kira gently wrapped her arms around Lara's waist from behind, her breasts pressing into her back. She leaned in close to her ear, whispering, "No, it is not Lara. I am your "biological" mother, Jack. Your mom here and your... father, dated in college, and hence she is intimately familiar with his sexual prowess."

Lara turned her head to face Kira, her eyes filled with love and tears. "Well, not just that. You see Jack, I was a very closeted person back than. My boyfriend at a time - your biological father, he sensed that I was not entirely comfortable with my sexuality and..." Her voice trailed off, "And it was him who introduced me to your mom." She hugged her wife and brought her into a kiss.

"Wait, so that guy impregnated you, mom, with me?" Jack asked Kira. "Well, we use artificial insemination method, but yes. When me and you mom decided to marry and have kids, he was the best option for a donor. And that is why I shouldn't and couldn't let you practice vaginal sex with me." Kira blushed, cause you are my "biological" son, and **** and all."

Jack was still confused, but he felt a bit more at ease knowing that it wasn't something terrible. "Why didn't you tell me before?" he asked, his voice slightly more gentle. "I always thought I was adopted, but I love both of you!"

"You do now, and we wanted to tell you when you are 21, it is just as a kid you could have had different reaction to this information, and we did not want to anyhow damage our family." Kira explained to Jack. "So, what do you think, Jack? Do you feel different now, knowing all this?" Lara asked him, her voice soft and tentative.

Jack considered the question for a moment, his mind racing with all the new information. He didn't feel different in a bad way, but he definitely felt like there was more to the story than he'd ever realized. He looked at both of his mom and smiled - "No, but I think want I feel is a need for another sex practice!"

P.S.
I wanted to drag it out a little bit more, where Lara uncovers Kira's cuckqueen fetish. And she teaches her son how to cuck his biological mother, with his other mother :) .
Lara and Jack would have sex everyday (and Kira would watch and masturbate), and sometimes Jack would be able to convince his moms to have lesbian sex, under the premise of learning about sex.

And in the end Lara would be pregnant with his child, and everybody would be super happy.