"I now declare you partners, soulmates and lovers for life."

It's a moment that Christine Forster and Virginia Flitcroft thought might never happen. Christine in a pantsuit with long jacket, Virginia in a navy, 1950s-style frock — standing in front of a wall of flowers waiting to say "I do".

And there, sitting in the front row is a family member who spent years campaigning against same-sex marriage: Christine Forster's brother, Tony Abbott.

Ms Forster and her long-time partner Virginia Flitcroft married on Friday in a cocktail party-style wedding in the centre of Sydney, overlooking the harbour and Botanical Gardens.

Former prime minister Tony Abbott joined his family on stage for group photos after the ceremony. ( Supplied: Dean Bentick )

The 200-guest wedding was attended by most of the Abbott family, including Tony and Margie Abbott, her mother Fay, sister Pip and nieces Louise and Bridget. Frances Abbott and bodybuilder fiance Sam Loch were unable to attend at the last minute.

Virginia's two children, Laura and Fraser Edwards, also attended.

In a show of support for his sister, the former prime minister mingled with guests, including many who were at the forefront of the Yes campaign.

The crowd mingled in the ballroom amid dark blue decorative accents and plenty of floral arrangements before the couple made an entrance.

Ms Forster and Ms Flitcroft arrived down a curving staircase draped in flowers as a song composed for the occasion by close friend and Australia's Got Talent runner-up Greg Gould titled All I Never Knew I Wanted, played.

Christine and Virginia share a laugh with their celebrant Kathryn Breusch during their wedding ceremony. ( Supplied: Dean Bentick )

"Are you two ready to get married? Shall we just do this?" celebrant Kathryn Breusch asked.

"[This is a] true expression of their love. Their day has finally come because of the big-hearted Australian people."

The audience laughed and cried throughout proceedings while Mr Abbott appeared to remain solemn throughout.

"I am forever changed by who you are and what you mean to me," Ms Forster's vows read.

"Without you, I can't be me."

Almost 200 guests attended Virginia and Christine's wedding. ( Supplied: Dean Bentick )

The vows were traditional in nature for the couple, who have been together for 10 years, before the women included their own personal touch.

"I take you Christine to be my wedded spouse, to have and hold, for better, for worse … to spend all my days at your side supporting you and your causes," Ms Flitcroft said.

It was the first high-profile same-sex wedding since marriage equality law was passed in Australian Parliament on December 7 last year.

The bill was passed almost unanimously to allow two people, regardless of sex, to marry, making Australia the 25th country to recognise same-sex marriage.

Mr and Ms Abbott joined in a family photograph on stage after the ceremony was over, smiling for the camera in support of the newlyweds.

"It's a great family occasion, very happy for Chris and Virginia and I'm looking forward to having a new sister-in-law," Mr Abbott said on his arrival at the wedding.

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Brides celebrate with Yes campaign anthem

Wedding guests included Liberal identities Dean Smith, who brought in Australia's same-sex marriage bill, Liberal MP Trent Zimmerman and Victorian MP Tim Wilson.

The nuptials kicked up a gear at the reception where iconic Australian comedian Bob Downe serenaded the couple during the bridal waltz with the song Love Is in the Air, the Yes campaign victory anthem.

Sorry, this video has expired Christine Forster, Tony Abbott's sister, arrives for her wedding with partner Virginia Flitcroft

Ms Forster and Ms Flitcroft were at the forefront of the campaign that gave unstoppable momentum to the success of the bill.

In stark contrast, Mr Abbott was a leading No campaign figure, labelling same-sex marriage as an attack on religious freedom.

More than 60 per cent of Australians voted Yes to recognising same-sex marriage — 7.82 million out of more than 12 million responses.

Tony Abbott sits alongside his mother Fay Abbott and wife Margie Abbott. ( Supplied: Dean Bentick )

Members of Mr Abbott's electorate of Warringah were resoundingly in favour of same-sex marriage, despite their local MP's sentiments, with 75 per cent of respondents voting yes.

"Obviously I'll be voting no, but this isn't about politicians, this is about the people, this is about your view," Mr Abbott told a media conference last year.

"If you don't like same-sex marriage, vote no. If you're worried about religious freedom and freedom of speech, vote no. If you don't like political correctness, vote no."

Ms Forster and Ms Flitcroft had planned to marry in the British consulate, but quickly decided to stage a full wedding as soon as marriage equality was recognised in Australia in December.

There had been some speculation as to whether Mr Abbott would be invited or attend.

Guests gathered around in the cocktail-style wedding to watch Christine Forster and Virginia Flitcroft say "I do". ( Supplied: Dean Bentick )

Watch Australian Story's Here Come the Brides on ABC iview.