In the X-men tie in short, we find out how Magneto found out about Wiccan and Speed's connection to him. The issue ends with him holding a picture of Wanda and Pietro next to his recently acquired picture of Wiccan and Speed.
In the sixth issue of Children's Crusade, as a distraught Scarlet Witch re-lives all the memories she lost, Wiccan reaches out to her, telling her of his and Speed's existence as her reincarnated children. Cue a heartwarming reunion, compete with mid air hugs, and a tearful apology from Wanda for forgetting them.
When Magneto first shows up and decides to take Billy and Tommy with him without stopping to first ask for their permission, both boys protest, but he more or less ignores them. Despite Magneto being one of the most powerful men on the planet, Teddy's having none of it, putting himself physically between Magneto and Billy and Tommy without hesitation even while acknowledging that it will amount to nothing if Magneto decides to employ violence.
Teddy: At the risk of your killing me with a single glance, sir, they're not going anywhere with you.