A society dominated by childless couples could become Australia's reality, with data analysis suggesting they will become the most common family type by 2023.

One sociologist says the trend is already happening, and future government policy will determine whether the traditional family model continues to exist.

For many millennials, like 23-year-old Karim Eldib, changing financial and social realities are important factors in the choice to have kids.

"[A lot of people] get the point where they say 'yep, going to have a child', and they don't think about all the things that come with having children," Mr Eldib said.

"I'm in a relationship and there has been talk of that but it's not something that we're seriously considering — it's something we'd like to consider after we've done all the things we want to do."

His view is shared by other couples delaying their decision to extend their families, a trend which paired with Australia's ageing population means the nuclear family is in decline.

The Australian Bureau of Statistics estimates between 2023 and 2029, there will be more people in a relationship living without children than families with kids.

Jackie Mahony and Trina Gilchrist, who are raising two-year-old Angus together, said the decision to have a child took a lot of thought.

"For us I think it's very much about should we just have the one child? One is easy for us," Ms Mahoney said.

"We've been in a really long-term relationship — 13 years coming on and Angus was certainly a part of that relationship and conversation," said Ms Gilchrist.

Future policy will impact family choices

University of Melbourne sociologist Leah Ruppanner said while the trend of not having children varies between countries, it is already happening in Australia.

"[The trend is most evident in] a lot of countries like South Korea and Japan, where their populations are shrinking because they are not having enough babies," Dr Ruppanner said.

"One of the things is governments need populations to grow because it means you have people paying taxes, people looking after the older generation, and people supporting the economy."

Bronwyn Harman of Edith Cowan University, who studies social responses to childless couples, said the public has become more accepting of non-traditional families.

"In the past, we had the traditional family of mum, dad and the kids — mum stayed at home, dad was the bread-winner. We know that's not true now," Dr Harman said.

She expects the 2016 Census data, which has not been fully released yet, will show an increase in households without children.

"I think if there are more couples without children in future or even people unpartnered, society will change with a change in policy and perspective," she said.

Early results from the latest Census are expected to be released next month.