Mariah Carey did NOT have any contact with her sister before she died ... because an alleged drug addiction drove a massive wedge between the two siblings.
Sources close to the situation tell TMZ ... Mariah never once contacted her sister, Alison, before she passed ... and instead spent the past week with their dying mother, Patricia.
Mariah was estranged from Alison ... and our sources say it's all because Alison suffered for many years from addiction. We're told Mariah tried supporting Alison, both emotionally and financially, but it wasn't enough to get Alison back on the straight and narrow.
Our sources say Mariah ultimately decided she needed to show Alison some tough love and not act as an enabler ... so she cut off her sister and put up a wall between them.
As we reported ... Alison died over the weekend -- on the same day as their mother -- without hearing so much as a peep from Mariah.
MC wrote about her relationships with her mom and sister in her 2020 memoir, "The Meaning of Mariah Carey" ... alleging Alison once "drugged me with Valium, offered me a pinky nail full of cocaine, inflicted me with third-degree burns, and tried to sell me out to a pimp."
For her part, Alison denied her sister's claims after the book was released.
No cause of death has been released in Alison's passing, nor in Patricia's.