SAME-SEX marriage advocates hope the Opposition Leader, Tony Abbott, will change his stance now that his sister Christine has come out as a lesbian and equal rights campaigner.
Christine Forster, one of three Abbott sisters, posed for photographs with her partner Virginia Edwards at a ''Lesbians in the (Opera) House'' event in support of same-sex marriage.
In an online photo gallery, Ms Forster holds an orange sign with ''I love her!! Marry Me??'' pointing towards Ms Edwards, who holds a sign: ''And I love her - live with it!''
Both had been married. Ms Forster has four children.
Mr Abbott's office said he declined to comment yesterday, but he told The Weekend Australian that he had kept his sister's confidence for four years.
And Ms Forster said: ''My brother and I have always had a strong relationship and he respects and supports me and my lifestyle choices.''
The national convenor of Australian Marriage Equality, Alex Greenwich, said advocacy from loved ones was the most effective way of changing hearts and minds.
''It is clear Ms Forster supports same-sex marriage,'' he said.
''She says as much. Ms Forster proves this issue is about family, love equality and not politics. It gives us hope that there is someone at the Abbott dinner table putting the case forward for same-sex marriage.''
Mr Greenwich said more than 45,000 Australians submitted, via the group's website and the political group GetUp, to a Senate inquiry that they support gay marriage.
''A majority of Australian people support same-sex marriage; therefore, more same-sex couples are comfortable with their cause. Blocking the reform is only going to get harder and harder for the Coalition.''
The NSW Gay and Lesbian Rights Lobby's senior policy adviser, Senthorun Raj, said same-sex marriage was not a minority issue but about justice and fairness for all Australians.
My brother and I have always had a strong relationship and he respects and supports me and my lifestyle choices
''The issue of marriage equality cuts across a range of families and communities in Australia.
"We hope this will signal to the Opposition Leader, Tony Abbott, the importance of allowing a conscience vote on the issue to ensure that same-sex couples have the same legal and formal recognition as heterosexual couples in Australia.''