After four decades with AC/DC, Malcolm Young, the group’s guitarist and founding member, is not returning to the band.
“Malcolm is suffering from dementia and the family thanks you for respecting their privacy,” his family said in a statement to PEOPLE.
In April, the group announced that Young was taking a break due to ill health.
“Malcolm would like to thank the group’s diehard legions of fans worldwide for their never-ending love and support,” AC/DC wrote on its website at the time.
In December, the group will release its 17th studio album, Rock or Bust, which is the first without Young in the group’s 41 years together.
“Unfortunately, due to the nature of Malcolm’s condition, he will not be returning to the band,” according to a recent statement from the group.
“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.”
• With reporting by MIA McNIECE and GILLIAN TELLING