WARNING: Major spoilers for Trial of Magneto #5 ahead!
The Scarlet Witch's parentage has always been a subject of passionate debate in Marvel Comics, but the recently released Trial of Magneto #5 firmly established Magneto as Wanda Maximoff's father, regardless of their blood connection. The event has shown that Scarlet Witch has seemingly been killed, and then resurrected, and the finale finds a way to create firm bonds between the father and daughter that make their relationship explicitly familial, something Marvel should have done ages ago.
Scarlet Witch and her brother Quicksilver started out as villains in the Brotherhood of (Evil) Mutants, where they were subjected to the abuse and manipulation of the Master of Magnetism. Slowly it was revealed that Wanda and Pietro were in fact Erik's children, and the three established a fragile but loving familial bond (that some might say was more akin to Stockholm Syndrome). However in the 2014 AXIS event the siblings parentage was retconned so that Magneto was not in fact their biological father, and both Wanda and Pietro weren't even mutants at all. Many fans disliked this surprise reveal, and it turns out that many Marvel writers did as well, because the relationship between Scarlet Witch and Magneto has continued to be consistently explored since their relationship's retcon.
In Trial of Magneto #5—written by Leah Williams with art by Lucas Werneck and David Messina—Wanda's entire murder was revealed to be an elaborate plot by Scarlet Witch to redeem the events of M-Day, which she directly caused. Wanda figured out a way to use her chaos magic to give Krakoa's Resurrection Protocols a major upgrade, allowing The Five to access Cerebro profiles for over 20 million mutants, long dead, that the X-Men otherwise never would have been able to resurrect themselves. In pulling off this amazing feat the Scarlet Witch finally establishes that she is Magneto's daughter, emotionally and magically, in a way that is impossible to deny in future storylines.
The spell that Scarlet Witch is casting requires three people, the offspring of the three founders of Krakoa, to create a magical link, so Wanda first gathers Lorna, Magneto's actual biological daughter, Legion, and Proteus, and yet the spell does not work. Lorna realizes that it is Wanda who should be the third participant in the spell, but Wanda doesn't think it's possible since she isn't biologically related to Magneto. Lorna asks Wanda if she considers her to be her sister to which Wanda wholeheartedly agrees before Polaris says, "You're just as much his daughter as I am." After attempting the spell again, it works, and Scarlet Witch is able to become "The Redeemer" in the eyes of mutantkind, proving that, at least magically, she is very much considered to be the daughter of Magneto.
The idea of "found family" is one of utmost importance in Marvel Comics, seeing as many characters have tragic family stories and instead have found community and love from the people they surround themselves with. Wanda Maximoff is no different, and this issue firmly establishes that regardless of what Magneto has done in the past. Wanda loves him like a father and Magneto loves Wanda as a daughter, even though she has been an enemy of mutants for years. Not only does Wanda continue to explicitly call Magneto "father" in this issue, but her sisterly relationship with Lorna is also solidified, further proving that Wanda, Magneto, and Lorna are family. The question of Pietro's relationship with Magneto is still up in the air though, as he's always had a much tougher time accepting Magneto as his father, due to the abuse he suffered at his hands. To see the entirety of the family drama between Scarlet Witch and Magneto make sure to pick up Trial of Magneto #5.