The couples used the three-course meal yesterday at Ms Gillard’s official residence in Canberra to lobby the prime minister to allow gay marriage.
Matthew Miller, 12, also presented Ms Gillard with flowers and two letters explaining why he and his brother Dylan, nine, would like their biological mother, Sandy Miller, to marry their “other mother”, Louise Bucke.
“Since they’re not allowed to get married, they’re basically being called not normal and we’re not known as a proper family,” Matthew said at Parliament House before the dinner, which the boys did not attend.
“I don’t know really why I am here,” he added. “To me, it is simple and this argument should have been settled long ago. People should be allowed to marry the person they love and to be accepted by all society.”
Along with Ms Miller and Ms Bucke, the other guests were Brisbane academic Sharon Dane, 54, who married Elaine Crump, 53, in Canada in a ceremony that is not recognised in Australia.
The third couple, Steve Russell, 51, and John Dini, 29, decided against marrying overseas because the move would carry no weight in Australia. While they could have a civil union recognised under state law in their home city of Melbourne, they don’t regard that as being equal to marriage.
Alex Greenwich, spokesman for the lobby group Australian Marriage Equality who was a late inclusion on the invitation list, said the dinner gave the guests optimism.
“We all got the impression that her [Ms Gillard’s] opposition was not immovable,” he said.
The activist group GetUp! paid A$31,000 (about £21,000) for the dinner after winning a bidding war against a Christian lobby group at the Press Gallery of Australia annual charity ball last June.
Ms Dane said afterwards she asked Ms Gillard why their marriage could not be recognised in their country of birth.
She said: “Apart from the sex of the people we’re attracted to, our feelings of love and commitment is not different to anyone else’s.
“The Prime Minister admitted that the more countries that embrace gay marriage, this puts pressure on Australia.”
Ms Gillard’s Labour Party lifted its long-standing opposition to gay marriage in December, and three separate bills have been introduced in Parliament that would change the Australian law which states that only a man and woman can marry.
But Welsh-born Ms Gillard personally remains opposed to gay marriage, and it is unclear whether any of the bills will attract enough support to make same-sex marriages legal. No date for votes in Parliament have been set.
A spokeswoman for the prime minister said: “The Labour Party’s position on this is clear. When the private members’ bills on same-sex marriage come to a vote, Labour MPs will be able to vote according to their conscience.”
Polls show that most Australians support gay marriage, but the conservative opposition coalition and many government MPs remain opposed.
Ms Gillard, 50, has never been married and is the first prime minister to live in the official residence with a partner, former hairdresser Tim Mathieson.