Williams, 49, made the revelation while talking about the close relationship pop star Madonna has with her son, Rocco, who is the same age as Williams' child Kevin.
"First of all, I want you to know, Rocco is 13 years old and Rocco is a real fan of his mother. What I discovered this weekend is that my son doesn't like me any more," E! News quoted Williams as saying.
"I discovered this a while ago, but the ball just got smacked home this weekend," Williams added, while wiping away tears. "He's all into his father -- you know how 13-year-olds are. I was the same way when I was 13, but it is breaking my heart.
"He says things to me like, 'Why are you so pissed?' But he'll say, 'Why are you so pissed?' Like I'm pissed all the time. Like I'm the one with the problem. ... He's the one that's 13, and I get it, and I know that this phase only lasts four years or something like that, but it is breaking my heart. He doesn't care about Wendy on TV -- he doesn't care about any of that. [Madonna's] lucky that [Rocco] likes her."