A matter of percentages

One hundred percent

The only claim of inheritance which can be made with absolute certainty is the result of a DNA test. A test taken by my late relative Dawn has consistently given this ethnicity result.

FTDNA test result 

Dawn's four sets of great-grandparents were quintessentially Irish and Australian:

Set 1 - McCarthy and Ryan were from County Limerick

Set 2 - Molloy migrated from County Limerick, Dwyer was from County Tipperary

Set 3 - Guinea was from County Limerick, Carney was born in Australia to parents from Tipperary

Set 4 - Halligan was born in Australia to Irish parents, and then there was de Chave. French ?  99% unlikely.

Dawn studied her family's origins before DNA testing was possible, so some family anecdotes were not disproven in her lifetime. What are the chances of doing so now?

Seventy-five percent likely

One of Dawn's great-grandfathers was John Henry De Chave. His name is recorded as such on a marriage certificate, his own [1], and a birth certificate, his daughter's [2]. He had a well-documented life in Grafton, New South Wales, between 1864 and 1874.

He was listed in the 1867 Samson directory for Grafton, and he appeared on the Grafton Electoral Rolls of 1869-70 and 1875 [3, 4]

but letters addressed to him in 1874 did not reach him. [5, 6]

Dawn recorded this family story in her research: 

John Henry DeChave died young. I have been unable to find any registration of his death. His daughter told her children that her father died when she was 8 years old.

Mary Ada Isabel, an only child, was born on 24 June 1866 and turned eight in June 1874, so this event could have taken place any time up until mid 1875.

Dawn's family held a photograph of her great-great-grandparents, the Henry and Margaret de Chave included on their son's marriage certificate:

This photograph was copied from one pasted into the Family Bible which was owned by Catherine DeChave (nee Halligan), later March, by her second marriage. It was labelled Great Grandparents by my mother. I strongly feel that it is of John [sic] and Margaret DeChave, but cannot be 100% sure.

 

Dawn's ethnicity measure means that they were Irish, and her family tree confirms this.

Fifty percent likely

Towards the end of 1874, around the time of de Chave's disappearance, a dead body was found in the mining area of Vegetable Creek (now known as Emmaville). de Chave had been involved in gold mining nearer to Grafton; in late 1873 the Vegetable Creek area saw an explosion in tin mining. 

The Tip-head near the Severn River was part of the Vegetable Creek tin mines. An enquiry about the dead body was held on 19 October 1874 by Robert Reid Cunningham Robertson, owner of Wellington Vale station, but did not result in a name. [7]

However, on 5 March 1878 in Glen Innes, De Chave's wife Catherine married a Vegetable Creek butcher, William March. [8] It can only be assumed that John Henry De Chave was dead. Was his the dead body found at Vegetable Creek ? 

All of the exploits of John Henry had fallen silent after 1874. One newspaper article in 1872 spells his surname as Shave:

Advertising (1872, April 9). Clarence and Richmond Examiner and New England Advertiser (Grafton, NSW : 1859 - 1889), p. 2. http://nla.gov.au/nla.news-article61878949

Would an Irish pronuncation of the surname Shea / O'Shea sound like Shave ? Both variants of this Shea  surname appear in the DNA match lists of other family members' genealogies. There is no evidence of another "de Chave" or its variations in various historical government repositories. 

Twenty-five percent likely

A common reason for using a pseudonym in the 19th century was to camouflage a convict crime. De Chave sometimes used Henry, and sometimes he didn't. Perhaps he was honouring his father?  Misdirectons?

In 1833, a Limerick man named Henry O'Shea arrived on the convict ship Portland after sentencing in a Tipperary court. Labelled as an indoor servant, his crime was stealing six tumblers. Servants were employed in "the big houses" and there was one in Tipperary County known as Marlfield House, owned by the Bagwell family over generations. 

O'Shea served his time of seven years. In 1848 he was working near Bathurst and he appealed to the Principal Superintendent of the Convicts' Office to reunite with his family - wife Barbara, daughter Caroline, and son John - by bringing them to Australia. [9]

They were in the care of Mrs Bagwell, near Clonmel. There appears to be no evidence of their arrival.  

In the photo of Dawn's great-grandparents, the gentleman is wearing a three-piece suit. The lady is wearing a decorated lace cap. Are they the garments of indoor servants who worked in Marlfield House, the Irish home of the Bagwell family ? They look grey-haired and well-fed. There is a carpet, drapes, and solid furniture. 

This rendering by Artificial Intelligence offers some tantalising interpretation.

AI image - colours are indicative only. [10]

Did Henry O'Shea return to Ireland? Was the photo taken after 1850? 

Did his son John travel to Australia on his own and stay, only to disappear in one of the isolated areas of the New South Wales ? 

There are other discrepancies which reduce the certainty of the possibility, such as the age John Henry gave on his marriage certificate - 23, as opposed to an age of 37 if calculated from the age given in Henry's appeal to reunite; the name of his mother - Margaret or Barbara; her maiden name - Ogilvie (which just happened to be a prominent family name on the Clarence River) or Barrett. Or was he trying to protect his family ? 

References 

[1] NSW Marriage certificate of John Henry de Chave and Catherine Halligan, #1865/2206. John's parents were given as Henry de Chave and Margaret Ogilvie 

[2] NSW Birth certificate of Mary Ada Isabel de Chave, #1866/8941

[3] The Clarence Electoral District, 1869-1870, ELE.1, Mackey Archives, Grafton Public Library

[4] The Clarence & Grafton Electoral Districts, 1875, ELE.2, Mackey Archives, Grafton Public Library

[5] No. 2. LIST OF LETTERS RETURNED FROM THE COUNTRY, AND NOW LYING AT THIS OFFICE UNCLAIMED. (1874, February 21). New South Wales Government Gazette (Sydney, NSW : 1832 - 1900), p. 557. http://nla.gov.au/nla.news-article223692919

[6] No. 22. LIST OF LETTERS RETURNED FROM THE COUNTRY, AND NOW LYING AT THIS OFFICE UNCLAIMED. (1874, December 8). New South Wales Government Gazette (Sydney, NSW : 1832 - 1900), p. 3704. http://nla.gov.au/nla.news-article223583275

[7] It hasn't been possible to substantiate a name for the dead body in the records of Wellington Vale station, A185. Held by the UNE Archives & Heritage Centre 

[8] NSW Marriage Certificate of Kate de Chave and William Newport March, #1878/5077

[9] Museums of Heritage NSW, State Archives NRS 905 Container 4/2844 Letter Number 49/278

[10] AI instruction developed by Andrew Redfern for photo restoration in Google Gemini, https://andrewredfern.com/juggling-family-history/