Not sure it's a story that needs to be told. It's easily handwaved as saying John Sublime donated the male component in their creation. Or perhaps there isn't a male component. I mean they were created in a lab that defies the very laws of time, space, gravity, and physics. Nothing is really a stretch at that point.
But does it add anything to the characters is the question. Right now the Cuckoos function basically as "rent-a-telepath" for teams that don't have Jean, Rachel, QQQ, or Betsy on them. They're a plot device to show that the team has some level of telepathic communication. Their current relationship with their mom is non-existent. It would just add a level of convolution for the sake of mild shipping between the donor and Emma.
Hello all! One of my favorite feats of Jean is from the early Gold/Blue team era, when she transfers her psyche to the mind of Emma Frost. AFAIK she's the only X-telepath to do so without artificial means. Add to the fact that she just had her telepathy recently restored, she was critically injured from two Sentinel blasts, and she managed to bring her telekinesis with her to boot. This wouldn't be the first time Jean does something to surprise Xavier regarding her capabilities
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