*rubs temples* I know that three issues isn't enough time to tell a full, coherent story. But, this was a mess.
Multiple people were backstabbing each other, all to bring about the climax where all these characters were standing on a flotilla of ships, addressing the demonic aspect of Illyana, revealing who all had betrayed each other. Illyana reveals that she had a child with some unknown mutant none of us have ever heard of before this miniseries, which raises a whole bunch of questions about Illyana's orientation and place in this world.
Personally, I have been an advocate for the idea that Illyana is ace. Throughout the 80s, she sometimes *talked* as if she were attracted to boys, but she never actually dated anybody. Ever. Male or female. Then, under Hickman, about five or six years ago she was written holding a group of aliens at swordpoint, demanding that they make out with her. There were both male and female aliens in that scene. Illyana then went ahead and murdered them all.
People like to talk about Claremont saying in interviews that he intended for Kitty and Illyana to be a thing. But, 1) that never actually happened in comics, 2) it would be wildly inappropriate if that ever did happen now, because Illyana would be making moves on her brother's ex-fiance, and 3) newbie fans need to understand that a writer's original intention NEVER matters in comics. Writers originally intended for Mr. Sinister to be an immortal adolescent boy, but that plan never came to fruition either. Original intentions are meaningless.
This hypothetical daughter by way of a male mutant is... A data point, I guess. Illyana is still being written as a rape-y bisexual, I guess?