"The majority of members are over 75 years of age," said John Freesmith, Mark and Maria's great-great-grandson.

"Some are starting to get health problems, which sort of spells the death knell of the reunions unless we can entice some younger ones."

Mr Freesmith said he would drive from Adelaide to attend the family reunion, and was expecting around 200 family members from Western Australia, Queensland and the Northern Territory.

In 1966, when members of the family were beginning to leave the area and farming, Mark and Maria's great-grandson, Jack Hayes, set about organising the first family reunion.

Mr Hayes became immersed in his family history, writing to England and the records office for information about his ancestors' movements.

"It's to Jack's credit really - the whole thing," Mr Freesmith said.

"He worked very hard to bring it all together. It's just sad to think that this tradition will die out."

Mr Hayes was Mr Freesmith's grandmother's cousin.

Before the first family reunion, the two had never met. Mr Freesmith's grandmother was an only child, and after she died in the 1940s, her children fell out of contact with the rest of the family tree.

At 19, Mr Freesmith had always had an interest in his family history, but knew very little of it.

In the late 1960s, however, he took a job at the Registrar of Births, Deaths and Marriages.

"I was like a pig in mud because I was able to get a lot of information which I was able to give to Jack," he said.

When Mr Hayes died in the 1990s, his daughter gave Mr Freesmith his correspondence so he could continue his work.

Mark and Maria were amongst the earliest European settlers in Victoria, eventually building a home in what is now known as the Hayes Reserve near Tooborac.

Mark was a founding member of the Heathcote and McIvor District Agricultural, Pastoral and Horticultural Society.

Despite their impact on the area, Mr Freesmith said the family reunions were more about the impact Mark and Maria had on their family.

"It's more about the values they distilled," he said.

"They had very strong Christian values. Very strong family values."

By the time of his death, Mark was able to set up his surviving sons with farms in the area, a tradition that was followed by at least one of his sons.

"It's a tradition of looking after your children and continuing the legacy of family support," Mr Freesmith said.

The reunion would be held at the Tooborac Hall on Sunday, 10 March 2024 from 10am to 4pm.

There would be ice-breakers, family tree displays, photos and afternoon tea. Clifford Hayes, former member of the Victorian Legislative Council would be speaking.

An invitation was extended to anyone related to the Hayes family, or any family friends from the last 170 years.

"There are so many people who are related in different ways," Mr Freesmith said. "They're all welcome."