The Gifted, Fox's upcoming X-Men TV spinoff, is more spiritually related to the mutant movie franchise than it is narratively. This world isn't meant to explicitly connect to any of the X-Men movies, but when it comes to Polaris, there's going to be at least one major similarity to her comic-book self.
Speaking to Comic Book Resources, The Gifted showrunner Matt Nix explained that the show's take on Polaris, a green-haired mutant with power over magnetism, will still be related to Magneto. This Polaris, Nix said, will have a history with the frequent X-Men villain that will be explored throughout the season while she also deals with "the baggage of mental illness".
There is some awareness she is Magneto's daughter -- I mean, her powers certainly are like Magneto's. That's something we will be exploring as time goes on, but more towards the end of the season, when some of these ideas and suspicions come to the fore.
She has to confront, "OK, if that's the case, what does it mean?" The idea is there are challenges and opportunities with that. In some ways, it might divide her from her friends. In other ways, does she accept the mantle of her birthright? Is it her job to be Magneto in his absence?
Magneto's had a lot of children across the various media that he's been depicted in over the years, and when it comes to his live-action appearances, Fox and Marvel have gotten rather creative in their respective approaches to his family tree. Most recently, it was revealed that the Scarlet Witch and Quicksilver, the twin villains-turned-heroes most commonly associated with the X-Men and the Avengers, are not actually Magneto's kids as had been canon for years. Instead, they are actually random people experimented on by the High Evolutionary.
It's thought that the change in their history was designed to distance the characters from the X-Men, to which Marvel does not hold the rights. This was complicated, though, by Fox and Marvel's decision to "share" the characters by splitting them up and staking claim to their cinematic appearances. The Scarlet Witch is currently a member of the MCU's Avengers (and her twin brother is dead), while a version of Quicksilver is zipping around Fox's mutant movies. Fox's Quicksilver is explicitly named as being Magneto's son, but there's no mention of his ever having had a twin sister. Instead, he has a much younger sister who's never acknowledged as being the Scarlet Witch -- and also a half-sister he doesn't know about, that Magneto fathered while living in Poland.
These are the sorts of complicated workarounds that happen when two huge companies have to play nice and share intellectual properties and, as is always the case, it's best to try and not overthink them.
The Gifted premieres in the US Monday, October 2 on Fox.