The late actor's family is now accusing John's son, Kelly Christopher Amos, AKA K.C., of isolating the "Good Times" star from his loved ones before his death.

In a family statement, John's relatives say ... "Over the past year, John Amos was isolated from his family and close friends by Kelly "KC" Amos, Eugene Brummet and Belinda Foster."

The family continues ... "Despite our repeated attempts to maintain contact, KC prevented access to him, controlled and monitored his calls and severed ties with John's daughter Shannon Amos, his brother Leslie "Syl" Franklin, his grandchildren Quiera Colston and Jhazz Williams, his business manager Paul Baldessare, his god-daughter Amy Goudy, his niece Sherri Korsun, his former accountant and other close family members, friends, and loved ones."

This group of family members released the statement, and they say "KC portrayed an image of a close father-son relationship on social media, but the reality was far more complex."

John's relatives say he suffered from dementia and claim "KC often gave John verbal prompts to create a narrative on social media that was not reflective of the truth. We were deeply concerned that our father may have been neglected and isolated during his final days as we received photos from concerned neighbors and a medical professional."

As we reported ... the family says they only found out about John's death through media reports this week, even though he died in August.

The death certificate, obtained by TMZ, reveals John was cremated 9 days after he died and lists KC as the one who informed the county of his father's death. The document also indicates KC has John's ashes.

John's family is questioning why they didn't hear about his death from medical professionals, the coroner, or authorities ... and accuse KC of not notifying them either.

The family adds ... "We believe there are critical questions that need answers, especially since we believe KC likely made the decision to have John Amos cremated without the family’s knowledge. We suspect these actions may have been taken to alter potential wills and collect life insurance or other benefits. This is made even more concerning by KC's struggles with addiction and mental health issues, as well as his previous arrests."

John's fam says they are "saddened and outraged" and "refuse to rule out the possibility of foul play."