WARNING: The following contains spoilers for Daredevil Annual #1 by Chip Zdarsky, Manuel Garcia, Le Beau Underwood, Chris Mooneyham, Rachelle Rosenberg and VC's Clayton Cowles, available now.
Daredevil just went through a massive - and secret - life change, all thanks to Mike Murdock finally forcing himself into Matt's life thanks to a powerful item. And Daredevil's former persona has now become a very real part of Matt Mudock's life as his biological brother.
In Daredevil Annual #1, these changes were caused by Mike Murdock rewriting reality with the Nord Stone is a tweak to Daredevil's origins, with Mike now having an accidental hand in leading to the death of their father that reframes everything that came later.
After stealing the Nord Stone from the Hood, Mike Murdock is able to use the reality-bending powers of the Asgardian artifact to make it so that he's always existed as Matt's brother and always had his own life within Daredevil's world. Growing up alongside his more studious brother, Mike ends up with a far harsher relationship with their father. He becomes something of a street grifter, eventually revealing his disrespect for their father partly over his habit of taking falls for gangsters and their bets. Matt later visits his brother on the street and convinces him, despite their problems, to come and see Jack in his next boxing match.
When he arrives, Mike ends up deciding to put a thousand dollar wager on his father to win the fight against the Fixer and the Owl. Mike's clearly saddened when he leaves and overhears the two criminals talking about Jack's commitment to throw the match -- and is just as surprised when his father actually fights and wins the match. The death of Jack Murdock has always been one of the ultimate motivators for his son to take up the mantle of Daredevil. His demise at the hands of criminal manipulators helped fuel his battles against the criminals who controlled the streets of Hell's Kitchen.
But it looks like in this newly reconfigured reality, Owl and Fixer weren't just killing Jack for failing them. Mike's massive bet on his father gave them a clear pause, but the Fixer was still confident that Jack wasn't trying to betray them for a big payday. But having Mike make such a large bet just before Jack decided to not take a dive likely gave the criminals plenty of reason to doubt Jack's commitment to them, and it could have been a reason why the Fixer ended up having Jack murdered. This could be seen as Mike taking a certain amount of responsibility for Jack's death, which Mike seems to believe, as the first thing he does after changing reality is to collapse into tears and apologize to the memory of his father.
This gives a whole new level to Daredevil's origins, as it makes the loss of Matt Murdock's father all the more personal. It was his brother -- not even acting out of spite or anger -- that led to the death of the man who raised them. While Mike may not have pulled the trigger, he was the one who may have helped point the gun at Jack Murdock in the first place. The rewritten reality isn't expanded upon past Jack's death, so it's not yet known if Matt knows the full circumstances of why Fixer turned on Jack. If Matt doesn't know, then this could lead to a pretty intense conflict between the two brothers, and it potentially makes Mike seriously regret the day he used the Nord Stone to create a life for himself and the effects it's had on the world.