For 31 years she has been married to Penny Whetton???, a climatologist who - when the pair met at university, fell in love and later married - was living as a man.

"We keep on talking about our relationship because it highlights how ridiculous our current law is, which says our relationship is lesser now that Penny has transitioned. But we are officially a same-sex marriage given she has transitioned," Senator Rice says.

Although the absurdity of the law might sometimes amuse the couple, it does not take away the pain of having to ask the Australian people if their marriage - which is longer lasting than many political partnerships, and predates by more than a decade John Howard's 2004 amendment to the Marriage Act - can be legally recognised.

"The fact is that gender and sexuality don't make any difference to a relationship. This is especially clear to me because I've experienced both a heterosexual and a same-sex marriage," Dr Whetton says.

Although transgender people are able to have passports that recognise their gender, only single people can apply to have their birth certificates changed.

Not being single, Dr Whetton never changed her birth certificate, which now sits in a drawer somewhere.

"We're going to be together forever," Senator Rice says firmly, but it pains her that her partner is "not able to fully affirm her gender".

"We went from being a stock standard, normal married couple to knowing society doesn't trust our relationship."

The couple - who have two sons - have faced public criticism of and hostility towards their marriage, as same-sex marriage has been tossed around for years like a political hot potato.

"There's knowing the bigotry is still out there and having to censor yourself. You never think about holding hands when you're a heterosexual couple. You realise there's still homophobia, transphobia, in the community. When you're a heterosexual couple people never judge your relationship or cast judgement on whether it's appropriate for us to have children," Senator Rice says.

While other people's perception of the couple might have changed, Senator Rice and Dr Whetton's feelings for each other never have.

Senator Rice shared her personal story in a speech in Parliament last month: "We used to kiss in public. But over the last 13 years we have self-censored ourselves. We generally don't hold hands in public. We got used to the fact that, if we are holding hands in the street, we need to be ready for the possibility of having a car driving past, wind down its window and hurl abuse at us. That's what the reality of being a same-sex couple in Australia still is."

Neither is particularly enthused about the public interest in their relationship, but both feel they have a responsibility to share their story as part of the campaign for a 'yes' vote on same-sex marriage.

While the pair's story is unusual, it is not unique - there's just no way to quantify how unique.

Although the Australian Bureau of Statistics keeps figures on the numbers of same-sex couples in Australia - at least 46,000 - it does not keep statisticson transgender people.

But both Senator Rice and Dr Whetton know how they feel.

"I can tell you that mine and Janet's relationship hasn't changed since we became a same-sex couple and we still love each other just like we did before. Our relationship is just the same as anyone else's - wonderful, loving and valuable. We're just waiting for the law to recognise that. It puzzles me that Australia is lagging on this issue. Let's just get it done," Dr Whetton says.

Senator Rice says since she gave her speech, ten couples have contacted her office saying they are in the same situation and thanking her for speaking out.

It is some small salve for the wound that is having to ask the Australian people to validate the couple's relationship.

The hatred Senator Rice has seen on her Facebook page since the postal vote was announced tells her the Greens were right to oppose the process from the start: "Having marriage equality is for couples like us. It strengthens the institution. It's about families. We have been married for 31 years and we want to stay married but our current marriage law doesn't allow that."

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