5. Was Palpatine Married?
Doing some quick math based on Rey’s age (19 during The Force Awakens) and how old she and her parents look in the flashbacks, we can guess that her father was born sometime in the decade before A New Hope. If we assume his son was conceived like 99.9% of humans in the galaxy (more on other options later), then at that time there was a woman in Sheev Palpatine’s life.
The easiest but least likely option is that Palpatine was married. We have never heard of a Mrs. Palpatine, not during his years as a Senator on Naboo nor Chancellor or Emperor. As the spider behind the web of politics and intrigue that came to envelop the galaxy, perhaps Palpatine did not want to let anyone close enough to mess up his plans.
Being as committed to the dark side of the Force as Palpatine was means his heart was filled with selfishness, concerned for his own interests. Love between two people is built on caring for their needs and wants, and a strong relationship comes from self-sacrifice. Based simply on that arithmetic it again seems unlikely he was in a romantic relationship.
That leaves conception via a less positive relationship. Despots and dictators throughout history and fiction have often kept slaves close to them for reasons of pleasure — for in-universe support, head over to Jabba the Hutt’s palace — so it’s not unreasonable to think Palpatine had a harem of sorts. He also may have kept women close with the goal of conceiving a child, which if true would seem to be a success in this case.
The ground seems ripe for another medium — likely a comic book series — to cast more light on Rey’s parents and even grandparents. Who was her grandmother, and how did she come to be involved with Darth Sidious? What was her story? Did she get to raise her son — and is that why he seems to be a person whose soul was not cracked and broken as his father’s was?
It’s slightly possible a level of retconning happens and an Empress is introduced, which would certainly be an exciting character to add into the galaxy. More likely we will find a woman in the shadows of galactic history.