The couple separated in January after 4 1/2 years of marriage. Aniston filed for divorce in March, citing irreconcilable differences.
"Aniston and Pitt had very little chance of lasting," Gray told The Associated Press. "They started out like the prom king and queen. He was the sexiest man and she the sexiest woman. That kind of pressure makes it hard to make a relationship last."
The former golden couple's split will be official Sunday, according to court documents.
Gray also doesn't hold out much hope for Pitt and Angelina Jolie, his "Mr. & Mrs. Smith" co-star. The couple have been photographed together in recent months with Jolie's two children, Zahara and Maddox.
"They're always under the microscope," Gray said. "And he went from one relationship to another so fast that there was little chance to be alone and find his happiness again."
Together, under media scrutiny, "they can't relax and make a relationship work," the 53-year-old California-based author said.
Gray will host a new talk show that will stream live on Internet radio. The show is set to debut in January on Modavox's VoiceAmerica network.
Has Gray's advice to others also worked for him?
"I'm healthy and wealthy and very happily married with three children. I don't offer simple solutions. Relationships are a challenge," he said.