It is clear from the film, and from anything you might care to read about Scott, that this man had a troubled youth, in and out of care (although his last foster parents are shown to be very loving), and it seems he has been in and out of trouble ever since the break up of his relationship with Liberace. 

The story is seen largely from his point of view: his initial awe and infatuation with Liberace; the ‘honeymoon period’ where they both get very fat; the plastic surgery and then the drugs to help him lose weight; the disillusionment and falling out; the denouement. 

Liberace was a totally outrageous, flamboyant man both on and off stage, with a great gift for piano playing but also for showmanship.  His mother says of him that Liberace was already greedy in the womb, leaving nothing for his twin who died at birth, just as in adult life he was greedy for approval from his audiences.  Certainly he is portrayed as having an almost insatiable appetite for success - and for sex, with a stream of younger lovers. 

The implication, though, is that Scott lasted longer than the others and meant more to Liberace, who had talked of officially adopting Scott.  He even underwent surgery to make him look like a young Liberace, swallowing a cocktail of drugs which started his drug addiction.  

We only have Scott’s word for all of this: publicly Liberace always denied his homosexuality and settled out of court with Scott.  When he died, Liberace’s doctor diagnosed heart disease but an autopsy by the county coroner revealed that he had died of AIDS, two years after Rock Hudson’s very public death from the same disease: however, neither man ever admitted to being gay.

These are three-dimensional characters, not caricatures: Liberace’s (surprising) Catholicism, Thorson’s love of animals, many facets go towards making these portrayals very believable.