Legendary Australian guitarist and AC/DC co-founder Malcolm Young has died aged 64.
Known for the powerhouse riffs and rhythm guitar that propelled the Sydney group to superstardom, Young had been "suffering from dementia for several years".
He was replaced by nephew Stevie for the band's last tour promoting the 2014 album Rock Or Bust.
Young started AC/DC in 1973 with his brother, fellow guitarist Angus.
Their other brother George Young, a member of The Easybeats and a producer for AC/DC, died in October aged 70.
Malcolm Young died peacefully on Saturday with his family by his bedside, a statement on AC/DC's Facebook page said.
"As his brother it is hard to express in words what he has meant to me during my life, the bond we had was unique and very special," Angus Young said.
"He leaves behind an enormous legacy that will live on forever.
"Malcolm, job well done."
Young told band to 'keep making music' after diagnosis
Young's family confirmed he was living with dementia in 2014.
In an interview with the ABC's 7.30, AC/DC lead singer Brian Johnson said Young had told the band to "keep making music".
"Without any of that sympathy stuff, you know, there was none of that stuff around.
"And he just said to keep doing it. That's the way he talked - [he was a] straight shooter.
"So we did, and it was great."
Angus Young said it was easy to tell when his brother started slipping.
"Malcolm was always very organised [so] it was kind of strange. For the first time I'd seen him disorganised, being confused about a lot of things," he said.
"That's when it kind of, you know, hit me. Something was not right with him."
Young is survived by his wife O'Linda and two children.