Tommy Lee's relationship with his son Brandon has been complicated for a number of years.

The 55-year-old musician and his 21-year-old offspring - whose mother is actress Pamela Anderson - were involved in a violent altercation earlier this week, which led to an investigation by the Los Angeles County Sheriff's Department, and a source close to the family has now revealed that they've had a ''difficult relationship'' for some time.

The insider explained: ''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.''

Tommy and Pamela married in 1995 and welcomed Brandon into the world the year after, when the Motley Crue star and the actress were at the height of their fame.

However, following their high-profile divorce in 1998, Tommy became a peripheral figure in the lives of Brandon and Dylan, 20, his second son with the former 'Baywatch' star.

The source told 'Entertainment Tonight': ''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.''

Over time, Brandon has made an increasing effort to build a closer bond with his dad.

The insider said: ''He wants better for his father. He wants to help him live a clean life and to mend their troubled past.''

But Tommy's new relationship with Brittany Furlan - who he became engaged to on Valentine's Day (14.02.18) - is said to have further angered Brandon, who believes the rocker has behaved poorly towards his mother.

The source added: ''Brandon resents that Tommy has chosen a fiancee that treats his mother poorly.''

Meanwhile, Pamela reportedly feels that her ex-husband -

who suffered a swollen lip in the clash with Brandon -

needs help to combat his drink problem and is angry that he's dragged their son into the situation.

An insider claimed: ''Pamela feels Tommy is sick and needs help for his alcoholism.

''She is furious that Tommy would blame his own son for his endless troubles.''