He may be one of Marvel's most infamous villains, but Magneto is also a family man. Many are familiar with Quicksilver and Scarlet Witch, Magneto's two children who joined the Avengers, but the Master of Magnetism actually has another child... and she takes after him much more than the other two.
Lorna Dane first appeared in X-Men #49 in 1968, exhibiting magnetic abilities similar to those of Magneto. However, while he was long suspected to be her biological father, it was not confirmed until Uncanny X-Men #431 in 2003. Lorna was born from an affair between Magneto and a woman named Suzanna. When Suzanna's husband found out, an argument erupted while they were on an airplane. Seeing her parents argue brought out intense emotion in the infant Lorna, which caused her powers to manifest. And wouldn't you know, her powers were the same as dear old dad's.
Unfortunately for Suzanna and her husband, Lorna's magnetic tantrum destroyed the plane and led to their deaths. It was then that Lorna's real father, Magneto, found her and had her memory altered so she would not remember causing the crash. Afterward, Lorna was raised by her aunt and uncle until they told her the truth when she turned twenty. Lorna eventually joined the X-Men after being discovered via Cerebro and fell in love with Alex Summers, AKA Havok. She originally went by Mangetrix until she settled on the moniker Polaris. Aside from instances of mind-control, Polaris is one of the good guys, unlike her father. However, she does work with Magneto in a few storylines. From 2000-2001, she was a member of Magneto's cabinet on Genosha, an island nation for mutants, and she fights alongside her dad in 2015's Secret Wars.
This raises the question: why did Polaris inherit Magneto's powers, while his other children have radically different abilities? In the case of Scarlet Witch, Marvel has changed the answer a few times. Most recently, Wanda's origin story was retconned so that she was never actually a mutant at all, but a sorceress who believed she was a mutant.
Okay, but what about Quicksilver? Super-speed and magnetism aren't exactly very similar. Well, mutant abilities come from something called the X-Gene, which is activated either by simply aging or by trauma. This is why Polaris's abilities appeared during her moment of stress on the airplane. There have also been instances of the X-Gene being forcefully activated through torture, like in Deadpool. The X-Gene can appear in anyone, but those born from mutant parents are more likely to have it and will usually inherit the same powers as their parents. However, more rarely, the offspring can develop different powers. Quicksilver is just one of those rare cases.
The TV series The Gifted on FOX features the first live-action portrayal of Polaris, played by Emma Dumont. Now, with the MCU reportedly figuring out how to introduce mutants, it's possible another version of the character may appear on the big screen in the future. Who knows, maybe Polaris will duke it out with her sister in the upcoming WandaVision series. They could even keep it in the family and get one of the Olsen twins to play her. Food for thought, people.