Anna Faris and Chris Pratt were "brought together" by their son's health issues.
The 40-year-old actress has recalled the "emotionally exhausting" weeks after little Jack's premature birth five years ago and how she and the 'Jurassic World' actor - who she split from in August - were warned the youngster could be "developmentally disabled" after he suffered a bleed on his brain.
In an extract from her memoir 'Unqualified' shared by People magazine, she wrote: "The pediatric neurosurgeon sat Chris and me down to tell us that Jack had some severe brain bleeding and there was a chance that he could be developmentally disabled.
"I was in complete shock ... So Chris and I did what we could, which was hold hands and hope and face it together...
"These moments can be hard on couples, but for us it really brought us together. It felt like it was us against the world."
Doctors warned the couple they wouldn't know for sure if Jack had suffered any lasting problems until he was around 18 months old, but he spent weeks being tested and examined in the neonatal intensive care unit.
And Anna, who had been on bed rest for a week before going into labour, said her mindset throughout the terrifying period became: "I have to be as strong as I possibly can ... I have to."
After around a month, the 'Mom' star and the 38-year-old actor were allowed to take Jack home, and he's grown up healthy, with just slight vision and leg muscle problems.
Anna wrote: "Today, Jack is at a beautiful age. He has some temper tantrums occasionally (did I mention he's five?) but he's a really good kid and he's happy and delicious and likes cuddles."
Tagged in Anna Faris Chris Pratt