Although Streisand is married to Josh's father, James Brolin, "She made it clear she would help Diane get everything she needed in her split from her own husband's son," a source revealed.
Both Josh and Diane have grown children from previous marriages and the source noted, "Barbra made it clear the divorce needed to go smoothly for the sake of the kids."
"The Way We Were" singer "knew that Josh was kind-of a nightmare husband,” the insider added.
2013 got off to a rough start for the W star, who was detained in Santa Monica just before midnight on January 1 for public intoxication after getting a little too involved in the holiday revelry.
“New Year’s, that’s what happened!” he laughed afterwards.
But no one was laughing in 2004, just four months after his marriage to Lane, when Josh was arrested for spousal battery. The actress called police claiming Brolin had hit her but she didn’t press charges.
This November, as Radar reported, Josh checked himself into rehab.
But Josh turned it down because Lane is reprising her role as Clark Kent's mother in the movie.
"He didn't want to make Diane uncomfortable," the source revealed.
"They're really going to be fine as a divorced couple--Josh admits he's too much of a 'bad boy' to be married to one woman and Diane and Barbra and even his father Jim agree completely," the source said.
"This divorce decision was really the best for the whole family."