Malcolm Young, who recently left AC/DC due to ill-health, is reportedly suffering from dementia.
61-year-old Malcolm Young, AC/DC guitarist and founder member, has been replaced in the band by his nephew, Stevie Young.
A family statement to People magazine said: “Malcolm is suffering from dementia and the family thanks you for respecting their privacy.”
AC/DC announced Malcolm Young’s departure last month but said they would go on without him and that their new album Rock Or Bust.
Rock or Bust will be released in December.
Malcolm Young, who emigrated from Scotland to Australia at the age of 10 with his family, formed AC/DC in 1973 with his younger brother Angus, who has famously dressed as a schoolboy onstage for many years.
The band has previously survived the death of their singer when Bon Scott died in 1980 after a night of heavy drinking in London. He was replaced by Brian Johnson, who has remained as vocalist ever since.
They have been a huge draw on the rock circuit for decades, creating anthems such as Highway To Hell and Back In Black, although they have tended to have album rather than single success.
AC/DC’s songs were used as the soundtrack for the movie Iron Man 2.
Their most recent release, 2008 chart-topper Black Ice, was only their third since 1990.