According to RadarOnline, Jules Stewart considers the British actor to be like a son and was devastated when reports emerged of Kristen cheating on him with Snow White and the Huntsman director Rupert Sanders.
A source said: "Jules is the glue that's keeping Kristen and Rob together. It ripped her heart in two when she saw those pictures of Kristen in a compromising situation with Rupert - and she couldn't believe what her daughter had done.
"As far as Jules was concerned, Kristen's relationship with Robert was a match made in heaven and she adored him like he was her own son. At first, she struggled to understand why Kristen wanted to cheat on him.
"But Kristen's young and Jules knows mistakes will happen - so she supported her daughter's efforts to win Robert back.
"She has been speaking with Robert, re-iterating Kristen's pleas for another chance and is trying to help build up trust between the pair. It is early days, but if this reconciliation can bring Robert and Kristen back together, they'll have Jules to thank."
The insider added that the couple's relationship is "weird", as Pattinson is still "not completely convinced that giving their relationship another chance is the right thing to do".
Last week, it was reported that Pattinson's family and friends are keen for him to move on from Stewart.
> Kristen Stewart, Robert Pattinson 'move back in together'
> Robert Pattinson has "deep connection" with Kristen Stewart
> Rupert Sanders, Liberty Ross 'in marriage counselling'
Photo gallery - Robert Pattinson and Kristen Stewart in pictures: