The 56-year-old actor and his 39-year-old wife Amal are expecting twins next month and Julia - who has twins Hazel and Phinnaeus, 12, and son Henry, nine with husband Danny Moder - insisted that the pair will be kept busy with their new arrivals.
Asked if she had any advice for them, Julia, 49, told Ellen DeGeneres: "It's gonna be so fun. They are a great couple and I think they don't need advice from me or anybody else.
"Also, you know, nobody's there with you at 3 o'clock in the morning when you're just going, 'What am I doing? Where did they come from and when are they going?' And then you sort of, you get through it and you figure it out and everybody does and it's a trial and error and a whole lot of tears and it's amazing."
Meanwhile, it was recently claimed that George is starting to get anxious about entering parenthood for the first time, but that he's nervous in a "good way".
An insider said: "[George] is getting a little anxious about the babies' arrival. But he's nervous in an excited, good way!"
And the source also claimed that the pair aren't thinking about their schedules just yet, as the 'Money Monster' star wants to stay with Amal at their home in Berkshire, England, until she gives birth.
The source added: "George is staying put until Amal gives birth. They'll figure out their schedules after that. For now, they're just hunkering down!"
Meanwhile, George recently revealed he and the human rights lawyer - who tied the knot in 2014 - haven't picked out any possible monikers for their children yet, as they don't want any names they choose to be ruined.
He said: "No we haven't picked out any names and I'll tell you why ... Because I've had friends pick out names around their parents and then it becomes ...
"Whatever name you pick they're like, 'Oh, I don't like that. That guy's a prime minister' 'Can't name her Susan. You remember your Aunt Susan?'
"[But] can you believe it?! Yeah, [I'm] even happier [than before]. I didn't know that we'd have kids. I was very happy that we were going to get married and then [a pregnancy] seemed like the next step."