As a self-described committed Catholic who does his best to go to church every Sunday, Liberal MP Andrew Wallace had always believed in the traditional view that marriage was between a man and a woman.
So when his daughter, Caroline, told him she had a girlfriend, it was completely unexpected.
"My wife and I were shocked," he told colleagues during a speech in the House of Representatives.
"I didn't know what to say. Homosexuality went against what I had been taught to believe for many years. How could this be happening? How could this be happening to me, to our family?"
Even though Mr Wallace has been fighting for stronger religious protections as same-sex marriage legislation is debated in federal parliament, he believes grappling with her sexuality only made his daughter's earlier battles with anorexia and bulimia even harder.
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"She said she had always secretly been attracted to women and I'm sure that this internal conflict would have in some part at least exacerbated her mental state," he said.
Mr Wallace will vote for the same-sex marriage bill and said his personal story about his daughter showed just how complex the challenge of legislating same-sex marriage is for federal parliamentarians.
"She said, 'Dad, in the years to come my generation will look back and judge your generation about how you deal with the issue of homosexuality in the same way that your generation considered your parents' generation in the way they dealt with our Indigenous people'," he told parliament.
Labor MP Linda Burney pays teary tribute to late son
For Labor MP Linda Burney, there are raw emotions tied to the same-sex marriage debate after her gay son, Binni, was found dead at their family home in Sydney last month.
"I support marriage equality as someone who has, and has had, loved ones who identify as LGBTIQ. To them, marriage equality would mean so much. I honour these people and in particular my late son, Binni," she said through tears during a speech in the House of Representatives.
In the emotional address, she said she had witnessed the confusion, anxiety and pain many young people experienced in dealing with their sexuality first-hand.
"Just as the 1967 referendum fundamentally transformed the way we talked about, and perceive, value and treat Indigenous Australians, I truly believe that the passage of the marriage equality bill will have a similar positive transformation on our nation," Ms Burney said.
Same-sex marriage is the main order of business in the House of Representatives this week with sitting hours extended to allow more than 80 MPs to speak on the issue.
