However, the pair are willing to wait potentially several more years before they tie the knot, declaring they won't get married until same-sex marriage is legalised in Australia.

Ms Stones said the decision to delay their marriage was made in support of LGBT friends and family who also have to wait in order to marry.

"It's personally important to us because we have many gay and lesbian family and friends, and we wouldn't feel comfortable to have them at our wedding and they couldn't get married," she said.

"It was important to make our stance in support of family and friends," Mr Duffy said.

While the Belconnen couple became engaged in December last year, the pair said it didn't change their stance in waiting until legislation surrounding the issue was changed.

They also said another reason for their stance was recently becoming parents for the first time, with Ms Stones giving birth to a boy, Henry.

"It's important because the government has mandated already that you have to say at weddings that the marriage means the union of a man and woman to the exclusion of all others ... which we don't believe and it's discrimination towards our loved ones," she said.

"Our decision is also a way of setting a good example to our son. We want to teach him to be respectful and stand up for what he believes."

The choice made by the couple to delay their marriage echoes a similar one made by ACT Brumbies star David Pocock and his partner Emma Palandri in 2011.

Mr Duffy and Ms Stones will talk about their decision at a forum at Dendy Canberra Centre on April 3, as part of a screening of the documentary The Freedom to Marry, which chronicles the decision made by the US Supreme Court in 2015 to legalise same-sex marriage.

Co-chair of Australian Marriage Equality Alex Greenwich said while it was unclear how many straight couples had made a similar decision, it was encouraging to see many taking a moral stance.

"It's a strong message that Australians value fairness and equality," he said.

"It sends a clear and strong show of support of the institution of marriage as an institution of love and commitment."

Mr Greenwich said he was confident of same-sex marriage legislation eventually passing through parliament, following a recent Senate committee report into same-sex marriage, which was signed by both major political parties.

"We're really hopeful because of the multi-partisan approach at the senate inquiry that we can achieve marriage equality," Mr Greenwich said.

With the federal government's preferred method of a plebiscite to allow same-sex marriage being voted down in parliament last year, it could be years until legislation passes that allows same-sex marriage in Australia.

However, both Ms Stones and Mr Duffy are prepared to wait until marriage equality becomes a reality.

"We certainly hope it won't be that long, but our family has been understanding of [our decision]," Mr Duffy said.