When Tony Abbott picked up one of Australia's major daily newspapers on Monday he would have seen his youngest sister on the front page passionately kissing another woman.

No surprises there. Christine Forster is openly gay and her big brother - the devoutly Catholic Prime Minister - has known for years.

Still, what he once regarded as a private matter is now very much out in the open as the mother-of-four emerges as a leading proponent of gender equality.

"I didn't go to get on the front page of the Age snogging my girlfriend," insists Forster of her appearance at last weekend's gay Pride march in Melbourne.


How did she react? "A rueful chuckle, I suppose."

The experienced journalist appreciates the benefits.

"Fantastic," she says, "in that it gave Pride a lot of publicity and that's what this is about. The more people we can get discussing this with their families and friends, the more attitudes can shift and acceptance grows."

This, of course, is same-sex marriage, which is now happening in 17 countries including New Zealand and Britain but, despite clear public support, remains illegal in Australia.

Forster says her brother has been "wholly supportive and non-judgmental" over her relationship with fiancee Virginia Edwards, but remains opposed to the couple's plan to marry.

"He knows he's not going to convince me of his viewpoint and I'm sure I won't change his mind," she says of their "diametrically opposing" views on marriage, which he believes should be only between a man and a woman.

Forster knows he's not for turning on that stance, but she has observed some change in the PM's attitude.

"After the last vote in Parliament he said he felt conflicted because of what he had seen in my relationship with Virginia," she says.

"I'm not going to speak for him, and I'm certainly not going to put words in his mouth, but I think it's illustrative of how any human being responds.

"If you're familiar with and up close to something like a strong, committed, loving, family oriented same-sex relationship then that is inevitably bound to break down reservations you might have about those kind of relationships under any other circumstances."

When Forster decided to leave her husband and conventional family life, Abbott and his wife, Margie, were the first kin she told.

She moved in with Edwards, another mother on Sydney's conservative north shore who had discovered her true sexuality.

They met while dropping off their sons at preschool.

"Obviously it was a shock to Tony when I told him I was in a same-sex relationship," she says.

Tony Abbott
Tony Abbott

"He was certainly surprised, but never judgmental, and only ever offered to support me in whatever actions I had to take."

Forster, who works as a senior writer at corporate information provider Platts, says her outing by the Australian newspaper in 2012 emboldened a move into public life and the heated public debate on marriage equality.

"I want you to know I'm a small 'l' liberal and a big 'L' lesbian," she declared to Liberal Party members before being elected to the City of Sydney Council.

Unlike the party leader, Forster supports a republic. She champions a woman's right to choose, describing herself as "unequivocally pro-choice".

The siblings share the same pragmatic streak. As pressure intensifies for another vote in federal Parliament, Forster hopes it won't happen this year.

Abbott has said his Liberal National Coalition colleagues will discuss their position should a private members' bill be introduced, but his sister fears defeat even if the MPs are allowed a conscience vote.

"There's understandably a lot of impatience, a lot of people feel like they've been fighting for this for an awful long time and I feel for them," she says.

"But we have to be realistic and acknowledge there's still a long way to go.

"I think we still have to do a great deal of work behind the scenes with politicians, and within Australian society in general.

"People need to be brought along so they can accept this reform, even if they don't agree with it, as something that is on balance a good thing for our society and nation."

The 49-year-old chooses her words carefully.

Although two of Abbott's three daughters have publicly backed gay marriage, she is reluctant to discuss the views of the family.

And although she accepts the right of former Abbott parliamentary secretary Cory Bernardi to express his opinion, she is horrified and offended by his comparison of homosexuality to bestiality.

"I would like to see those kind of attitudes absolutely eradicated from the Liberal Party," she says.

Despite the increased profile, Forster is playing down political ambitions. "I think two Abbotts in federal Parliament might be a bit too much for everybody," she says.

As for her wedding, she believes it's a case of when and not if. And Tony will be there, alongside drag queens who will replace the bridesmaids.