In his new memoir, Elton John opens up about his relationship with Michael Jackson, and how it changed over the years.

Although Elton John was friends with Michael Jackson for a time, things began to change as the late singer got older.

“I’d known Michael since he was 13 or 14,” John wrote in an excerpt from his forthcoming memoir Me, which was published by The Independent. “He was just the most adorable kid you could imagine. But at some point in the intervening years, he started sequestering himself away from the world, and away from reality the way Elvis Presley did.”

“God knows what was going on in his head, and God knows what prescription drugs he was being pumped full of, but every time I saw him in his later years I came away thinking the poor guy had totally lost his marbles. I don’t mean that in the light-hearted way. He was genuinely mentally ill, a disturbing person to be around,” he added. “It was incredibly sad.”

John went on to describe a dinner party he once threw, which Jackson had been invited to.

John recalled that Jackson, who wouldn’t eat anything, dismissed himself from the table, and they found him later on with their housekeeper and her 11-year-old son.

“For whatever reason, he couldn’t seem to cope with adult company at all,” John wrote.

Earlier this year, new allegations were made against Jackson in the Leaving Neverland documentary by Wade Robson and James Safechuck, who claimed in the HBO film that Jackson sexually abused them both as children.

The star, who died in June 2009, repeatedly denied any wrongdoing prior to his death, and in 2005 was acquitted in a child sex abuse case leveled against him in California.

The Jackson estate has sued HBO and slammed the Emmy Award-winning documentary, which calling it “another rehash of dated and discredited allegations.”

Me will be available on Oct. 15.