Michael Buble and his model wife Luisana Lopilato have announced that their eldest son, Noah, 3, is battling cancer.
Buble, 41, released a statement saying the family had a long road ahead and asked for privacy while they dealt with the diagnosis.
"We are devastated by the recent diagnosis of cancer of our oldest son Noah, who is currently receiving treatment in the United States," he said on Facebook. "We've always talked a lot about the importance of family and the love we have for our children."
"Luisana and I will devote all our time and attention to help Noah to get better, for now suspending our professional activities," he said. "During this difficult time, we ask you to pray for him and please respect our privacy.
"We have a long road ahead and we hope that with the support of our family, friends, fans around the world and our faith in God, we can win this battle," he said.
It is reported that Noah was thought to be suffering from the mumps until doctors did further tests.
It is unclear what type of cancer he has or at what stage.
In June 2015, Noah sustained "serious burns" to around 6 per cent of his body after an accident involving scalding water.
Buble was in the US when his wife rushed their son to Hospital Alemán in Buenos Aires on June 25.
Buble told ET the day after: "He's okay. It's tough to see him go through it. I try to remind Lu that we are lucky. That it could have been worse."
The Canadian musician and the Argentinian actress and model welcomed their second son, Elias, into the world in January.