Uncovering the past! Toni Collette discovers tragic secrets from her parents' troubled childhoods on Who Do You Think You Are

She is well-known for her role in Little Miss Sunshine as a member of a dysfunctional family, but in real life, Toni Collette has an equally unconventional family.

On next Tuesday night's episode of SBS's Who Do You Think You Are, the Australian actress uncovers details surrounding her parents' less than perfect childhoods.

'I wanted to do it for myself,' the 42-year-old told News Corp Australia of why she participated in the show. 'But I also really wanted to do it for my kids and my folks. I had no reservations whatsoever.'

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Troubled parents' pasts: Toni Collette stars on next week's Who Do You Think You Are where she uncovers secrets from her mum Judy and dad Bob's lives

Troubled parents' pasts: Toni Collette stars on next week's Who Do You Think You Are where she uncovers secrets from her mum Judy and dad Bob's lives

In the episode, Toni, who has two children, Sage Florence, 7 and Arlo Robert, 4, with musician husband Dave Galafassi, found out some surprising new information about her maternal and paternal grandfathers.

Growing up, Toni knew that her maternal grandmother Ivy had died hours after childbirth, collapsing on the newborn baby and suffocating her to death.

After the tragic death, Toni's widowed grandfather, Joseph, chose to split his four children up and sent them to live in separate homes.

Startling details: In the episode, the 42-year-old finds out surprising information about her maternal and paternal grandfathers

Startling details: In the episode, the 42-year-old finds out surprising information about her maternal and paternal grandfathers

New discovery: The Academy Award nominee, pictured here with her father, discovered the man she believed was her paternal grandfather was in fact, not biologically related to her

New discovery: The Academy Award nominee, pictured here with her father, discovered the man she believed was her paternal grandfather was in fact, not biologically related to her

'I wanted to do it for myself' Toni said she participated in the show for herself, but also for her family - her two children Sage Florence, 7 and Arlo Robert, 4, and musician husband Dave Galafassi

'I wanted to do it for myself' Toni said she participated in the show for herself, but also for her family - her two children Sage Florence, 7 and Arlo Robert, 4, and musician husband Dave Galafassi

In search of answers, the blonde beauty traveled to Bathurst, NSW. There Toni became more empathetic towards Joseph as she discovered some surprising revelations about the situation. 

'It humanised my maternal grandmother,' the Academy Award nominee explained. 'We’d all made assumptions about the kind of guy he was. We were wrong.'

The visit exposed the truth - her grandfather had believed he had no choice but to give up his four children. Alone after they left the family home, Joseph had fallen into a life of crime, alcoholism, drugs and homelessness.

Searching for answers: Toni traveled to Bathurst, NSW to find out why her maternal grandfather Joseph split up his four children after his wife's death

Searching for answers: Toni traveled to Bathurst, NSW to find out why her maternal grandfather Joseph split up his four children after his wife's death

The episode also detailed Toni's discovery that her believed paternal grandfather was, in fact, not her father's biological dad.

Instead, Toni learnt that her biological grandfather was an unnamed American serviceman, whom her grandmother had begun an affair with after ending her marriage.

'I was very close to her,' Toni said of her grandmother. 'Coming to understand her as a woman with needs and desires rather than a superhero has been massive for me.'

No qualms: The blonde actress said she had no reservations doing the show and that learning more about your family, ultimately means learning more about yourself

No qualms: The blonde actress said she had no reservations doing the show and that learning more about your family, ultimately means learning more about yourself

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