Warning: Minor spoilers for Marvel's Daredevil below.
While Sister Maggie is presented as a figure from Murdock's past, the show later sticks to comics continuity when it reveals that she is actually his mother who left his family when he was a baby, joining the Catholic Church as a nun.
In a flashback sequence, we see Sister Maggie suffering from postpartum depression while Matt is still a baby. She is taken to the church and Matt is left in the care of his father Jack Murdock. Jack raises the child until his eventual murder at the hands of mobsters when Matt is a young man, eventually sending him to the church.
When Sister Maggie tells the story, she reveals that she has been a nun for 30 years. Given how old Matt is when she leaves the family to join the church, we can reasonably assume that Matt himself is around the age of 30 years old, maybe a bit younger.
The new episodes explore Murdock's background in great length, beyond Stick's training that set him up for the fight against the Hand, and more explanation for why he decides to fight in against seemingly impossible odds.
That's partially the reason why Daredevil decides not to call his allies in the Defenders or the Punisher in order to take down Wilson Fisk; it's a fight he has to take on his own, a mistake from his past he has to correct. Showrunner Erik Oleson addressed these characters' absence during an interview with ComicBook.com.
"Well, there's a number of reasons," Oleson began. "There's the story reason of that Matt feels that it is his responsibility that Fisk's release in large part is on him for not having taken care of it the first time around, or the second time around. And so Matt Murdock is determined to right the wrongs that he himself set in motion.
"He also, in a kind of a spiritual way, feels like God is speaking to him and is putting in front of him a raison d'etre, a reason to keep going and to keep existing after his heartbreaking life turn at the end of Defenders, where he walked out of the building, Elektra did not. And in episode one of this season, Matt essentially attempts suicide by thug. So he has spiritual and emotional reasons for why he doesn't call in the Defenders."
Fans can watch Season 3 of Daredevil, now streaming on Netflix.