I have been riding this prediction since I saw Force Awakens. This is mostly because, at the time, it would have been so unexpected. Everyone was so focused on Ray Solo or Rey Kenobi, etc, that I was, and still am thinking Lucasfilm will want to pull out something unexpected to give a little of that “I am your father” WOW moment. After all, Palpatine certainly had a harem of some sort. There would likely be offspring that someone might have been able to get a baby or two out of there. This would not be a big concern for Palpatine at the time, as he was all-powerful. Rey could be Palpatine’s granddaughter, or great-granddaughter. Or perhaps a clone using Palpatine’s DNA. I can’t explain the gender difference on that case, but cloning technology in a galaxy far, far away was not in my school curriculum, so I am just going to accept that gender selection would be possible.
Overall, I think with episode VIIII bringing Palpatine back, the idea becomes more likely and this less startling.
This post is based on my answer to a question on Quora. Check that out here:
What would your reaction be to Rey being a Palpatine? Answered Apr 21
Testing this commment system