Jennifer's friendship with the actor/director pre-dates her five-year marriage to actor Brad Pitt, which ended in 2005.
And after George, formerly one of Hollywood's most eligible bachelors, wed British human rights lawyer Amal Alamuddin in 2014, the couple became parents to twins Ella and Alexander three years later.
During an appearance on "The Ellen DeGeneres Show", which is set to air on Thursday, December 06, the "Horrible Bosses" star spoke of how thrilled she is that George is now a proud parent to the 18-month-old twins.
"It's amazing to see him with children," the 49-year-old actress smiled to the host. "That's what we talked about: that anything can happen."
However, when questioned on just how old her friend's children were, Jennifer was forced to confess, "I don't know," before she tentatively guessed, "Maybe a little over a year? Maybe?"
George's likelihood of becoming a parent was low, as the "Ocean's Eleven" actor, who was once wed to actress Talia Balsam, had famously wagered a $10,000 (£7,800) bet with pals Cindy Crawford and Michelle Pfeiffer that he would never marry again.
"There's something about Steve Carell that everybody loves deeply; you can't not just love Steve Carell," she told Ellen. "Dramatic beautiful actor, that movie 'Beautiful Boy' is just stunning, he is fabulous, such a range of emotion."