Judging from Luke and Leia's birth, procreation in the Star Wars universe works basically as we'd expect on Earth (but with robot midwives). Having now learned that...
Rey, I am your grandfather
-- Darth Sidious
...I'm puzzled as to when they procreated. I don't recall seeing evidence of them even having a prior relationship nor having a family. It's also a bit hard for me to imagine this character finding a partner, having sex(*), parenting, etc.
Question: At what point in the Star Wars timeline did this character become a parent?
I'm perplexed as to where it fits into the Star Wars timeline, especially:
Did pre-resurrection or post-resurrection Darth Sidious become a parent?
(*) Apologies for the mental image.