One was a black warrior, the other a white Irish convict. "They still exist today in modern times, their spirit is still with us through our descendants, through our families," Paul House, the great, great, great grandson of Onyong the warrior, said. "Their identity, belonging and connection to country comes through us all as modern day people."

Liam Cotter, great, great grandson of the white man, Garrett Cotter, said when his family honoured Onyong with a plaque at the original Cotter cottage high on the range between the Murrumbidgee and Naas rivers more than 25 years ago, some people questioned history.

"So I would like to thank Paul's family for recognising and acknowledging, not only the plaque, but the relationship that existed all those years ago," Mr Cotter said.

A new book to be launched at the Canberra Writers Festival on Saturday brought the families together on the land Onyong had revealed to Cotter. Its author Richard Begbie was at the gathering, overjoyed to be with them on Mount Macdonald.

"Onyong died in 1851, or 1852, Cotter in 1886," Begbie said. "There was no one who knew this country like either of those men and I think that probably remains true today. No one would have covered that country on foot in the same way as Onyong did and Cotter," Begbie said.

Cotter: A Novel [Longhand Press] begins about 1822. "I had written 100 pages before Onyong suddenly appeared, and he sort of snuck his way into the story and then, I don't say he took it over, but it really then became the story of these two men, and that's how the book ended up, as the story of these two men," Begbie said..

Having written extensively of the high country throughout his years with the Canberra Times, in the children's adventure story Tennant's Gold, and in a recent biography, Max Oldfield: The Story of his Ride, Begbie relies on extensive historical research, his time in the Naas Valley with Cotter's great grandson Bill Cotter, and the novelist's imagination for this book.

Reading from Cotter, Begbie recounted the assigned convict working near a creek near Lake George, building cattle yards when he encountered Onyong for the first time. He was already on alert after earlier seeing a bloated, dead, white man at Lake Bathurst speared in the back for trying to take away young Aboriginal girls.

"Although he had heard no sound, he suddenly stiffened with the clear sense of being watched. Nothing malevolent, just watched. Slowly he turned around and for a moment could recognise what he had seen all day, drag marks of timber in the dirt, the shimmer of heat on the bare ground, the darkness of forest rising in the distance. Then out of this remembered scene there slid into relief a dark, still figure, not 20 yards away."

The man was not like the blacks in the camps. He was tall, much taller than Cotter, sleek and well-muscled. "His stance was easy, still as a tree. His right hand was closed around a spear, its cruel barbed end pointing to the heavens."

Over many years their friendship led to Cotter's name being attached to the valley, river and dam supplying Canberra's water. Cotter in turn was able to provide shelter for Onyong at vulnerable moments in later years.