Best known for playing Brian Tanner on the alien puppet sitcom - which was a huge hit when it ran from 1986 to 1990 - was found dead in his car alongside his service dog Hans at a Chase Bank parking lot in Peoria, Arizona, on 13 June, but his passing only emerged publicly on this Wednesday night.
Benji's sister Rebecca told TMZ the actor had suffered from depression, bipolar disorder and was afflicted by an insomnia disorder that often kept him awake for days.
The Maricopa County Medical Examiner's office confirmed Benji's death, but has not yet determined a cause.
TMZ reported: "Those close to Benji believe he went to the bank to deposit residual checks on the 12th, fell asleep in his car and tragically died from vehicular heatstroke due to Arizona's intense summer heat.
"Benji was with his service dog Hans, and the animal also died."
His death certificate has confirmed the death of his passing, and the Maricopa County Medical Examiner's Office said Benji's cause of death is still pending.
Rebecca added to TMZ Benji's family is "grieving a great loss" and she "appreciates everyone's thoughts and kind words".
She wants donations in Benji's to be made to either The Actors Equity Foundation or the American Society for the Prevention of Cruelty to Animals.
Benji starred in 101 episodes of NBC's 'ALF' - the plot of which told of the middle-class Tanner family who take in alien ALF after he crash-lands in their garage.
The series shows the Tanners struggling to hide the extra terrestrial from nosy neighbours and government officials.