Samuel Johnson's life has been tainted by more tragedy than most.
But the star says he didn't truly comprehend the enormity of the loss of his mother Merrill to suicide when he was just three until he began reading through the letters written for his latest – and what he calls his "most intense" – book yet, Dear Mum.
"It built this picture of just how important they are and exactly what they mean to us," the 43-year-old tells Woman's Day, breaking down when asked what he'd say to Merrill if she were here now.
"I love you. I'd just give her a big hug and I'd have a million questions."
Luckily, Sam says he's found surrogate mums in the form of his sisters, Hilde and the late Connie – who passed away from cancer in 2017.
And also in the mother of his late girlfriend, Lainie, who also took her own life in 2006.
"She's become a mum to me," he tells Woman's Day.
"We've never been out of touch. I'm popping over for more cups of tea."
And while it would be understandable if the breast cancer advocate, whose charity Love Your Sister has raised more than $13 million for medical research, preferred to shy away from Mother's Day, he says he's always used the occasion "to celebrate Hilde and Connie, because they're both shockingly good mums."
Curated over three years and with contributions from a cavalcade of Aussie celebrities, including Guy Pearce, Amanda Keller and Patti Newton, Sam says he was determined to get Dear Mum right.
So, what would his mum think if she could see him today?
"She'd be possibly proud," he says.
"In the poem that she wrote to me a couple of months before she died she instructed me: 'All the seas of joy rise to sing for you boy, surge and swell and roar.' I've tried to be like the ocean and do nothing but surge and swell and roar."