Morgan Carey hasn't spoken to his sister in two years. Still, he claims that he has never seen her sober and he worries she is going to “die like Whitney Houston”.

Rumours of the 45-year-old suffering from depression and alcohol dependency have surfaced before, particularly last summer around the time she split from husband, Nick Cannon, 34.

Speaking to the National Enquirer, the star’s younger brother said that he feels Mariah is not fit to look after her four-year-old twins because of her substance abuse issues. He also claimed that she is taking a number of medications on a daily basis.

“Mariah was drinking through her pregnancy, even while she was nursing… I can’t say that I have ever been around her when she was sober, and that’s very scary. “

This is not the first time one of Mariah’s siblings have spoken out in the media.

Her 53-year-old estranged sister, Alison, has also talked to the media on a number of occasions. Most recently, Alison spoke to Star magazine in January – at the same time that Nick was filing for divorce from Mariah after six years of marriage.

Alison, who is a former prostitute and has a history of drug abuse, told the magazine that she was reaching out to her younger sibling, and that she did not want money – despite Mariah being worth some €450m.

She added that she was desperate to meet her niece and nephew and that she wants her famous sister to love her again.

“There’s been a lot of water under the bridge. I’ve done things that were wrong. She’s done things that were wrong.

“But I’ve reached out to her many, many times through the years in every way I could think of to try and ask for her forgiveness and see if we could start over. We are the only sisters each of us will ever have.”

Alison, who has been living with HIV since 1988, has also said she is broke and is struggling to support her two children. 

However, according to a 2006 statement from Mariah’s rep, the superstar is “looking for Alison to want to help herself”.

“Mariah can be there with love and support,” the rep added, “but at what point do you not enable someone any longer?”

Her rep furthermore said that Mariah has paid for rehab on a number of occasions for Alison.

It is not known why or when Mariah and her brother Morgan became estranged.

Morgan is also clearly not a fan of his sister’s ex, calling Nick “a crock of s***” and saying that he was only ever interested in her money.

“Nick was there for the cash from day one. He doesn’t give damn about Mariah.” 

When the siblings' parents divorced in the early Seventies, Mariah and Morgan remained with their mother, Patricia, while Alison went to live with their father, Alfred.