Inside Tommy Lee and Son Brandon's Complicated Relationship (Exclusive)

A source tells ET that the pair's relationship has been difficult from the start.

Tommy Lee's relationship with his son, Brandon Lee, has been complicated for many years, a source tells ET. 

The father and son recently made headlines after an altercation led to a criminal investigation by the Los Angeles County Sheriff's Department, but ET's source says "they have always had a difficult relationship."

The issues between the pair dates back to childhood. As a founding member and the drummer of Motley Crue, Tommy spent much of Brandon's childhood touring with the band or working on other music projects. According to ET's source, Tommy's career, which took him all over the world, is one of the reasons for his and Brandon's complex relationship.

"Tommy thinks Brandon resents him for working so much when Brandon was young, and he likes to believe that has caused most of their issues,” the source claims.

Tommy and Pamela married in February 1995 and welcomed Brandon in June 1996, at the height of their fame. Their second son, Dylan, was born in 1997, but the couple divorced just one year later in 1998. Tommy and Pamela were off-and-on over the next decade before splitting for good in 2008.

"Pam raised the boys for the most part on her own. [Tommy and Pam] divorced when the boys were very young, and Tommy didn't make himself available to the boys," ET's source says. 

Tommy and Brandon at the X Games in Los Angeles in 2003. - Chris Polk/FilmMagic

Despite their history, Brandon started staying with Tommy part-time, in part to attempt to strengthen their bond. "As Brandon has grown older, he has tried to build a positive relationship with his father,” ET's source says. "He wants better for his father. He wants to help him live a clean life and to mend their troubled past."

The source also claims that disagreements over Pamela have further strained Brandon and Tommy's relationship. "While Brandon wants to help his father, he wants his mother to stay far away from his father," the source says. "He wants Pam to cut all ties.”

Tommy and Brandon at Guitar Center in Hollywood in 1997. - SGranitz/WireImage

Tommy's new relationship has also apparently deepened the strain. The 55-year-old musician got engaged to former Vine star Brittany Furlan, 31, on Valentine's Day this year, who appears to butt heads with Pamela. "Brandon resents that Tommy has chosen a fiancee that treats his mother poorly," the source alleges.

Then there are Pamela's feelings based on her history with her ex. "Pamela supports her boys' decision to help their father, but sadly she has never seen a change in Tommy's behavior and worries about her sons' false hope. Pamela wants them to have the best father they can...but also knows they need to see their father for who he really is," the source says.

ET's source adds, "Pam hopes Brandon will take a step back and let Tommy realize he needs to build a healthy relationship with his son.”

"Pamela feels Tommy is sick and needs help for his alcoholism," the source claims. "She is furious that Tommy would blame his own son for his endless troubles."

ET's source claims that Pamela and Brandon aren't the only ones concerned about Tommy's health. "Right now, many of Tommy's friends are worried about him. While out to dinner the other night, he looked exhausted. He was very pale and very thin," the source says. 

"He likes to live his life like a 20-year-old rock star, and he clearly isn't taking care of himself. Brandon and Dylan were recently staying with Tommy part-time and trying to help him get sober," the source claims. Brandon also discussed organizing an intervention for this father in his statement following the incident.  

Tommy has denied that alcohol played a role in the incident between him and his son. Instead, he believes his boys have been "poisoned" against him by Pamela, among other claims outlined in a lengthy statement.

As for what's next for Tommy and Brandon, the Los Angeles County Sheriff’s Department tells ET that Tommy filed a report with the LASD claiming a public offense was committed by Brandon. The LASD is taking that as filing a formal criminal complaint. ET has learned that the investigation remains ongoing and Brandon has sought legal representation and that Brandon and his attorney are cooperating with the investigation.

Reporting by Adriane Schwartz.