Christine Forster, Prime Minister Tony Abbott's sister, has painted naked in an embrace she shared with partner, Virginia Edwards, for artists Robyn Ross' entry to the Archibald Prize of 2014.
Forster, Sydney's Liberal councilor, said his brother will just probably ride along to this.
"I think he'll think, 'Good on you, Chris. Go for it," Forster said.
Forster's and Abbott's view on same sex marriage are at different poles but the former knows Abbott will always be conservative about his views on marriage.
"He believes in marriage as it is defined in the Marriage Act and I don't think he'll ever change his personal view but what he will do is listen to his party," Forster said.
"He has signaled that marriage equality is open for discussion in the party room. I think the people within the Liberal Party are of the view that they should have a conscience vote on marriage equality," she added.
Forster noted she was struck by how artist Ross captured her intimacy with her partner Edwards in the painting titled, "Ladies in Waiting."
"It captures that closeness and it's a lovely message of support. The message is right there for all to see. I genuinely think the painting reflects how most Australians feel about the issue of same-sex marriage - that it's a no-brainer," she cited.
The two have been together for six years and engaged in March 2013.
The Archibald Prize is one of Australia's most favorite and prestigious art awards. The very first Archibald Prize was given in 1921.
"The Archibald Prize is a who's who of Australian culture - from politicians to celebrities, sporting heroes to artists," according to the Web site of Art Gallery NSW.
The award is given to the best portrait painting each year with preference to some men or women distinguished in art, letters, science or politics, painted by any artist resident in Australasia. The trustees of the Art Gallery of NSW will choose the winner among the applicants. Those who made it to the list of finalists will be displayed in an exhibition at the gallery.