Malcolm Young's family have confirmed the musician is suffering from dementia.
Founding member of the rock band Ac/DC was announced as retiring from the band last week, struck down with the incurable brain condition.
In a statement to People his family said: "Malcolm is suffering from dementia and the family thanks you for respecting their privacy."
Linda, the rocker's wife is believed to have made the decision to move Malcolm to a care home in Sydney.
Malcolm's nephew Stevie Young is to replace him as rhythm guitarist in the rock band as they go on tour next year.
A statement read: "AC/DC will undertake a world tour in support of 'Rock or Bust' in 2015. Stevie Young, nephew of founding members Angus and Malcolm Young, plays rhythm guitar on 'Rock or Bust' and will accompany the band on tour."
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