Cousins are disappearing. Is this reshaping the experience of childhood?

Noelene Lancastle grew up surrounded by 27 cousins and 10 second cousins. They were a range of ages and had what seemed like a world of experiences, always ready to teach her to skateboard or swim, help carry heavy boxes, play with her on camping trips or have her back in school in North Delta, B.C.

"There were always lots of kids around. You know how your parents dragged you around to houses? There were always some kids for us to play with that were somehow related to us," Lancastle, 46, said from Vancouver.

It's something her own children won't experience.

Lancastle's older brother and sister don't have children and her husband is an only child. So Nicholas, 9, and Charlie, 7, don't have any cousins at all — a growing trend as the decreasing fertility rate causes extended families to narrow over time, sociologists and demographers say.

Worldwide, families are shrinking, according to a kinship study published in December in the Proceedings of the National Academy of Sciences USA. That study, using international demographic data for every country in the world, projected a 38 per cent global decline in living relatives for individuals aged 65 by the year 2095, compared to 1950.

The composition of family networks is also expected to change, with grandparents and great-grandparents living longer, but the number of cousins, nieces and nephews declining, the authors noted.

"Canadian children nowadays have fewer cousins than previous generations," said Rania Tfaily, an associate professor in sociology at Carleton University in Ottawa who studies social demography and contemporary changes in marriage and family formation.

This isn't a recent phenomena as fertility rates have been decreasing for some time, added Tfaily, who was not involved in the kinship study.

"However, what is striking nowadays is not just that the number of cousins is declining but also that an increasing number of children are growing up with no or very few cousins."  

And it's part of the reason Lancastle decided to have two children, despite having them later in life.

"I could have been a one and done person," she said. "But they would have no relatives that would be their age. So I wanted them to have each other, at least."

Canadian data obtained by CBC News from the researchers of the kinship study projects that the average Canadian 15-year-old girl will have just 3.6 living cousins in the year 2095, compared to 15.3 in 1950 — a 76 per cent decrease in living cousins.

Using demographic data, the researchers computed kinship structures for every country in the world from 1950 to present, and then calculated projections to the year 2100. The model is based on a hypothetical person from the population, in this case, a woman of a specified age.

A Canadian woman aged 35 would have had about 20 living cousins in 1950, while a woman the same age would have half that — 10 living cousins — in 2020. By 2095, a Canadian woman aged 35 is projected to have just five living cousins, according to the data.