Despite divorcing nearly 18 years ago, Jessica Simpson and Nick Lachey continue to engage in petty disputes and display animosity toward each other, according to insiders.

The 42-year-old singer and her 49-year-old ex-husband rose to fame with their 2003 reality show, Newlyweds, which documented their tumultuous marriage, eventually leading to their divorce in 2006.

"However, the animosity between them persists, and they argue about everything," says a source. "She still considers him impolite, and he thinks she's a ditz."

When Jessica's TV pilot based on her successful memoir, Open Book, was recently canceled, Nick reportedly reveled in her misfortune. "He can be quite petty," the insider claims.

At the same time, Nick's show, Love Is Blind, has faced criticism, and Jessica has reportedly told mutual friends that "he deserved it for being so conceited." Nick's response, according to the source, is that she should "keep her mouth shut."

Furthermore, while Nick, now married to actress Vanessa Lachey, 42, insists he has never read Jessica's memoir, he allegedly discusses it often. "He's fixated on it, and it must infuriate Vanessa," the insider reveals.

Jessica Simpson and Nick Lachey's relationship history shows they were a prominent couple in the early 2000s. They met in the late '90s as their careers took off and married in 2002. Their MTV reality series, Newlyweds: Nick & Jessica, propelled them to stardom, but their marriage faltered, and Simpson filed for divorce in 2005.

After their separation, the pair met one last time, and Lachey played his then-new album for Simpson, with all the songs about her. In her 2020 memoir, Open Book, Simpson described feeling "numb" and "manipulated" during that encounter, leading her to sleep with him.

Simpson and Lachey finalized their divorce in 2006, and both have since moved on. Lachey married Vanessa Lachey (née Minnillo), with whom he has three children, while Simpson found love with former professional football player Eric Johnson and also has three children.

In the years following their divorce, both Simpson and Lachey have discussed their relationship and the reasons behind its dissolution.