And now, Radar has exclusively learned some of the stunning reasons why, including Stiller's fixation on another woman and his hypochondriac attitude about his health which ruined his sex life with Taylor, a source said.
"It was Ben who was to blame for the marriage breaking up," the source said of the scandal.
Recently the couple has been fighting over Stiller's "close friendship" with a female friend he had met on a movie set, according to Radar's source.
"Ben became quite taken with her and was often heard bragging about how talented the woman was and he gushed that she was 'definitely going places!'" the source said.
"His wife Christine was not amused by her husband's mid-life infatuation and the couple fought constantly about it, especially in recent months—because Ben stayed in touch with the gal and claimed he was only 'mentoring' her."
The source noted that Taylor "didn't believe a word of it! And Christine threatened Ben with an ultimatum: 'You stop talking to her.' "
At first, the There's Something About Mary star complied, the source said, "but then Christine caught him on his cell in covert conversations at all times of day and night. When she confronted her husband, he replied, 'You will not censor who I talk to. Back up give me my space!
"Christine blew a gasket!"
Also, Stiller, 51, and his actress wife, 45, who played Marcia in The Brady Bunch movie, had trouble with their sex life.
Stiller survived prostate cancer in 2014. The tumor was surgically removed and Stiller told Howard Stern that he has been cancer-free ever since.
But the source said, "After the scare he and his wife hardly shared a consummated marriage!"
Plus, after prostate cancer, Stiller "has been on a roller coaster ride of self-pity. He's become a hypochondriac and every few months swears the cancer is back. He drove his wife crazy with all his constant complaining and erratic behavior. Christine had no choice but to pull back."
The source said "every time Christine tried to help, when he grew more and more anxious, he began slamming doors, breaking thing, and throwing temper tantrums in front of their two kids and friends."
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