The former Governor of California and his wife Maria Shriver split earlier this year after she discovered he had a 13-year-old love child with their housekeeper Mildred Patty Baena and while Kirk is a family friend, he admitted he was surprised at the revelations as the couple's youngest son Christopher is the same age.
He told Seven magazine: "Well we knew he was a bad boy but my wife Anne and I had been with Maria and him about two weeks before the revelations came out that he had another family, so yes we were surprised. That's bad management on his part.
"Well you know a movie star has easy access to a lot of things."
Despite his own lothario reputation, Kirk has been married to Anne for 57 years and he credits her with saving his life in 1958 by stopping him from getting on private plane because it wasn't safe.
He said: "I was so mad, I still wasn't speaking to her the next day. Then we heard on the news that the plane had gone down and everyone on board had been killed."