Samuel Johnson has made a touching tribute to his late mum while launching his latest book, a book of letters to mums.

He shared his story on his charity Love Your Sister's Facebook page, which raises funds for cancer research as his oldest sister Connie battled the disease before passing away.

Johnson shared that his mother took her life when he was just three years old.

He told his followers that she left him a handwritten poem, that reads:

All the seas of joy,

Rise to sing for you boy,

Surge and swell, and roar.

All the seas of joy,

Sound wonderfully near,

Since you've been here.

"That was my mum. Some crazy poet lady who found life a most onerous undertaking," Samuel wrote.

"There exists only one photo of me and my mum, and that's always OK because I have that poem, burnt into my heart."

He said that his older sister Connie felt the impacts of their mother's suicide more deeply than he did.

"From a very early age, she was determined to become a mum and to see her kids through," he continued.

"She was extraordinary. Connie became the mum our mum could never be, to two young sons. Now, like me, her boys are motherless."

Connie died at age 40 after battling cancer three separate times in her lifetime.

Dear Mum is a collection of letters written by famous Aussies, including Amanda Keller, Peter Helliar, Rebecca Gibney, Patti Newton and many more.

"It serves as a fitting homage to mums and the importance of them ... it's a beautiful montage, for all kinds of mums," Johnson explained.

"I put everything in on this one. And now I think of it, I'd like to dedicate this book to my mum. I suspect she'd be pretty puffy about this one."