Joaquin Phoenix and Rooney Mara speak about baby son for 1st time

Joaquin Phoenix and Rooney Mara are speaking publicly about their baby son, River, for first time.

The Oscar winner, 46, and his Oscar-nominated fiancée, 35, shared that they were first-time parents in an op-ed about the migrant children crisis the pair penned for People magazine.

The notoriously private couple named their son River in honor of Phoenix's late brother, Hollywood star River Phoenix, who died in 1993 of an accidental drug overdose at age 23.

The child's birth was revealed by documentary film director Victor Kossakovsky at the Zurich Film Festival on Sept. 27 following a screening of the documentary "Gunda," which Phoenix executive produced.

In their emotional op-ed, the couple addressed recent news reports confirming that parents of 545 children separated at the border by immigration officers haven't yet been found. "The weight of that number is staggering. Five hundred forty-five children," they wrote.

"As new parents, it's unbearable to imagine what it would feel like to have our child taken away from us for a day, let alone years. But that's the very situation those 545 children and their parents have been living through," they continued.

As part of the Trump administration's 2018 "zero tolerance" policy on undocumented immigrants, border officers separated 2,800 families that year. More than 1000 parents were separated from their children in a pilot program the year before.

"The practice of taking children away from their parents at the border was intended to be a deterrent. Many of the families subjected to it were asylum-seekers — meaning they came to the U.S. looking for our help after fleeing violence and danger at home," the couple wrote. "Instead, in order to send a message to other families who were on the run, we took their children away from them hoping that word might filter back home that new peril awaited anybody looking to make a similar journey."

"In some cases, this meant quite literally ripping children younger than 5 out of the arms of their parents, even babies under a year old," they continued.

Phoenix and Mara argued that "the damage will be lifelong" for the children.

"Child psychologists say that even short periods of forced removal from the care of a parent can cause irreparable emotional harm," they wrote. "Some of these children are no more than toddlers or have yet to reach their 10th birthday. Our hearts break to think about the suffering they've endured at our country's hands."

The pair concluded their op-ed by wondering how they'll ever explain the crisis to their newborn son.

"We have to ask ourselves: Is this the country that we want? Are these our values? How will it feel to explain to our son, when he asks us about this time and how we treated scared, defenseless children, some of whom may never see their parents again?" they wrote.

"For the sake of our nation's character," they added, "I hope we will be able to tell him that America unequivocally rejected this cruelty and demanded that our representatives did everything in their power to find those missing parents."