WARNING: The following contains spoilers for X-Corp #3, on sale now.
In theory, the mutant island nation Krakoa is meant to be for all of Marvel's mutants. However, there are still a few holdouts who have chosen to remain elsewhere instead. One of those mutants is former X-Factor member Layla Miller, who burst into the Marvel Universe in Brian Michael Bendis and Olivier Coipel's House of M #4.
Now an adult who's married to one of Jamie Madrox's duplicates, Miller hasn't joined the rest of mutantkind on their island paradise because she's achieved a rare milestone for anyone associated with the X-Men. She's retired from superheroics, living the dream of the MCU's Wanda Maximoff, but it didn't come easily.
Layla is no stranger to calamity. As a child in the Marvel Universe, was initially an enigmatic, and mostly unwanted, presence in the X-Factor mutant detective agency. While she aided X-Factor Investigations, she clearly had her own agenda, which she never shared with the rest of the team. The closest she came to revealing her motivations was what became her catchphrase, "I know stuff." One of the things she knew was that she'd eventually marry Madrox, which was a disturbing thing for him to hear from a 12-year-old. It turned out that Layla's knowledge came from time travel. Layla traveled to the future with one of Madrox's duplicates during the Messiah Complex crossover and wound up stranded there.
Layla would eventually return to the past as a fully grown adult, downloading her memories into her younger self's brain in the process. It was too much for her younger self to fully take in, leaving gaps in her knowledge. During a trip to the future with her, Madrox learned the truth about Layla's powers.
In reality, Layla had the mutant power to resurrect the dead, which came with a price. Anyone she resurrected came back without a soul. They retained their memories and personality but lacked any empathy. In the future, that turned the mutant Fitzroy into a supervillain. When she returned to X-Factor, she resurrected teammate Strong Guy. His lack of empathy eventually led to him having a falling out with teammate Monet St. Croix, which caused him to leave the team. It put him on the road to murdering Wolfsbane's son Tier and becoming the King of Hell at the end of the Hell On Earth War.
In the aftermath of the war, X-Factor Investigations went their separate ways. In X-Factor #262 by David and Neil Edwards, a demonic Madrox, transformed by Mephisto, and a pregnant Layla wound up squatting on Madrox's family farm. Intervention from Jamie's old flame Theresa Cassidy, who had become Celtic Goddess The Morrigan, turned Jamie human again. The Morrigan gave Madrox the chance to reform X-Factor. He declined, choosing to retire with Layla.
While Madrox has made multiple comebacks, Layla has remained retired. It makes her a rare figure in the Marvel Universe. Her story was told in X-Factor, but it didn't end in her death. She's been allowed a happy ending that includes life beyond superheroics.
While she is able to focus on things like raising her and Jamie's son Davey, Madrox's attention is still split. In Tini Howard, Valentine De Landro, Sunny Gho & VC's Clayton Cowles X-Corp #3, Layla calls Madrox to let him know that their son Davey is about to take his first steps. She wants him to delegate his duties to one of his staff of other Doctors Jamie Madrox so he can see this milestone moment in person.
The prime Madrox appearing in X-Corp is more of a workaholic than previous versions. Instead of leaving one of his duplicates in charge of the project, he sends one through the Krakoa Gate so he can absorb their memory later. Madrox's plan fails miserably on both fronts. The generator overheats due to an oversight on Madrox's part, and the dupe with the memories of his son's first steps is incinerated venting it. Unfortunately, Madrox's memories of Davey's first steps went with that duplicate.
While her husband finds himself split between the worlds of superheroes and suburbia, Layla Miller has the relatively normal, stable life that has eclipsed so many other Marvel heroes, from WandaVision's Scarlet Witch to Spider-Man. And given what he just missed, Madrox may very well start thinking about taking cues from his better half.