The film climaxes with Lennon finding his rawest feelings of abandonment in the context of Primal Scream therapy, then recording 'Mother' as a record of his pain, and - in what may well be a fabricated dramatic moment - using the recording to directly confront his wrinkly old codger of a dad about his dereliction of fatherly duty.
As an aside, I have to add that Barbra Streisand, whose own father died when she was about a year and half old, recorded a showy version of the tune:
While Lennon's life story was ultimately about abandoning the parents who originally abandoned him, the Doors' film (which contained no actors, only footage of the band) showed how frontman Jim Morrison reported his entire family were dead. Morrison's claim was a lie of course, but in a way it was also true: his father George was ideologically dead to him. While Jim was spreading a gospel of free love, free drugs and hedonistic pacificism, George was fighting for his country. He was an Admiral in the American Navy.
There are multiple levels in these narratives. Both stars emerged in an era where a generation gap was establishing itself around the formation of a counter-culture. Both men rejected their fathers and joined that culture, becaming its icons.
In the familial rejection argument - which seems reductive but still convincing on many levels - Lennon's personal struggle is projected outwards to become his political protest. The confrontation of his childhood demons is also the culmination of his quest for musical authenticity.
Jim's loss of intimacy with his family, meanwhile, becomes a desperate quest for something that he can never quite find. He is let down by the hypocricy of the media, the falsity of stardom, the vacuuity of his fans, the cheap thrill of casual sex, and, ulimately, the false comfort of drugs and alcohol. Morrison's chronicles his lack of trust and a failure to find true intimacy. Despite having more adulation than most people can dream about, he is therefore romanticized a tragic rebel whose dreams were never fulfilled. Indeed his personal quest for freedom from the shackles of society was miscarried because it was pursued in the absence of any rewarding sense of intimacy.
Of course their struggles feed back into their own myths. After all John and Jim were just eligible and troubled young men begging to be loved. Meanwhile, fatherhood is the missing term from the lexicon of rock'n'roll. It is the present absense around which the adolescent ego pleasures of the form cohere. The 'double fantasy' of popular music is that fans sometimes dream they can create the intimacy missing when their heroes engage with the alienated process of stardom. In this context evidence of the celebrity's tragic childhood act as vouch-safe for an ego need which is taken to drive their quest for fame.
Psychologists say that we learn more in the first four years of our lives than in the rest. Jim Morrison often said that when he was four he witnessed a traumatic road accident where some Native Americans were killed. I doubt it ever took place. More likely, Jim created a glamorous poetic mystery by fusing a crucially early but mundane failure of parental availability (like his mother being ill or in grief) with one of America's most potent myths: the car crash as a masculine metaphor for the frenatic, breakneck pace of life - the obsession with speed symbolized in James Dean's death smash and chronicled by Paul Virilio and others.
So, then, what can we say of these bad boys of rock? They lost their parents at a young age, lived fast, died young, and numbed the pain with the playful outlets - sex, drugs and rock'n'roll. If you don't want to end up like them, just keep your eyes on the road and your hands upon the wheel.