Frances Abbott has thrown her support behind the Yes campaign for marriage equality, speaking about her desire to see her aunt, City of Sydney Liberal Councillor Christine Forster, able to legally wed.

The youngest daughter of former prime minister, and same-sex marriage opponent, Tony Abbott, appeared in a video for Australian Marriage Equality released on Tuesday morning.

In the video, Abbott, who works as a personal trainer, discussed her aunt's relationship with partner Virginia Edwards.

"I look at Aunty Chris and I don't think she planned to fall in love with Virginia," Abbott said in the video. "It just happened."