Their relationship has grown stronger since both couples have become parents.
The Clooneys welcomed twins, Alexander and Ella, in 2017, while the Duke and Duchess of Sussex had their first child, a son named Archie Harrison, on May 6.
In a recent interview with the DailyMail, the "Catch-22" actor said he can't remember how his friendship with them started but it's been a number of years.
He and Amal attended their royal wedding last May and have hosted the newlyweds at their Lake Como villa.
The Clooneys also have a home in Sonning, Berkshire, which is not far from Meghan and Harry's Winsdor cottage.
"We live not too far from one another and we have dinners and stuff and we’re friends with them for all the reasons that you’re friends with anybody," the Oscar winner said.
"They’re just really nice, fun, kind people, they’re a very loving couple, and they’re going to be great parents."
Clooney said of his twins' personalities: "They’re really funny and really smart."
"We’ve decided because we spend a lot of time in Italy and they’re going to spend a lot of time growing up there, that Italian is going to be one of the languages they learn," he explained. "Already they’re saying their ABCs in Italian and in English."
"And they can count from one to 20 in Italian too, which I can’t do! They’ve definitely got my wife’s genes in the brain department because she’s the smart one in the family."
The actor said that his new family life has shifted both his and his wife's priorities. Although Amal is a prominent international human rights barrister, she is more cautious about the type of cases she takes on.
"She’s as tough as nails and she’s going to keep doing what she believes is the right thing to do," Clooney said.
"She’s had an incredibly successful career and accomplished some amazing things, so she’s not going to curb what she’s doing. But we’ve got kids together now, and we talk about things."
He revealed: "'We talk all the time about which clients she gets called about, whether she takes them on or what cases would be too dangerous."
The entertainer has agreed to as well pull back on his charity work that takes him into dangerous areas of the world. "We’ve made certain pacts about how she’s going to stop going to certain places, and I said I’m going to stop going to war zones where it’s dangerous to be."