MICHAEL KEATON is  still reeling from the cancer death of his beloved ex-wife, the mother of his only child.

The 58-year-old actor and his ex, Benson star Caroline McWilliams, divorced in 1990 after an eight-year marriage, but the two were still close.

Both Michael and their son Sean were at Caroline’s bedside when she passed away at age 64 in February, sources say.

"Michael HAS NOT married again and a part of him never stopped loving Caroline," a close family friend told The ENQUIRER.

"He was her rock during the last days of her illness, and now he’s helping their son Sean cope with the terrible loss."

Caroline started out in the daytime drama Guiding Light and became a regular on the breakthrough ABC hit Soap playing Sally. She later played Marcy Hill opposite Robert Guillaume on Benson.

After their divorce, Caroline put her career on hold to look after Sean, now 27 and an aspiring actor, the source said.

"At first there was bitterness between her and Michael. Especially when his career was red-hot and he was dating Courteney Cox," the source divulged. "But in time they drew close again because of Sean. In the end, they were each other’s best friend."

During her final days, Caroline suffered terribly as the disease spread, the source added.

"It was heartbreaking, but Michael and Sean were there for her every minute," the source said.

"Michael told a pal, ‘Caroline was everything a mother should be. She’s the reason Sean turned out to be such a terrific kid. I see her every time I look at him.’"

Keaton – who starred in Beetlejuice and Batman  – is now riding high as the voice of Barbie’s boyfriend Ken in Toy Story 3.

"When the film was in production last year, Michael brought over a Ken doll and kept Caroline laughing doing Ken’s voice at her bedside," the source said.

"Caroline didn’t live to see the finished film. But Michael said he thinks that she’s up in heaven smiling – and looking after him and Sean."