Macaulay Culkin's father Kit and stepmother Jeanette Krylowski fear he is "heavily into drugs," or that he is seriously ill.
The former child star has been pictured looking gaunt and thin, clutching his stomach and appearing to vomit in the street and his estranged father Kit and stepmother are worried for his health.
Krylowski told The Sun newspaper: "Kit has seen the photo. But he can't talk about it. He just can't, because it hurts him too much. Of course he's worried, he's incredibly concerned.
"When I saw the photos I thought, 'Oh no, this is not good. Either he's dying of some disease or he's heavily into drugs.' "
Home Alone star Culkin quit acting aged 14 and later had his parents blocked from legally controlling his $21 million fortune, leading to the breakdown in his relations with his father.
The actor, now 31, lives a reclusive life in New York, and it has been claimed he has a $7,300-a-month drug problem and an addiction to painkiller Oxycodone, which could kill him in the next six months.
Krylowski added: "Now we're hearing he is denying the allegations - but it certainly looks like he is on drugs. He looks awful.
Culkin has been caught with drugs before, being given three one-year suspended jail terms in 2004 after he was arrested for possession of marijuana and controlled substances Alprazolam and Clonazepam.
Krylowski says the breakdown of his family - which suffered a further blow when Culkin's sister, Dakota, was killed in a car crash in 2008 - has badly affected Kit, and he is no longer able to lead a normal life, and is himself a near recluse.
She added: "Kit is pretty sensitive. I was there during the custody battle. That tore his soul out. Kit is a lot different than the happy-go-lucky Kit that I knew in the 70s. There's a deep, deep hole that's never going to be filled.
"We don't live off a penny from Mack. We live off benefits. But we live simple. We're happy."