Sir Robert Harley (1661-1724) Earl of Oxfordshire and Earl Mortimer, is the 6th Great Grandfather of Linda Davison right up to the 12th Great Grandfather, Richard Harley (1235-1260) and even earlier. That is 18+ direct Generations of the Harleys of Brampton Bryan through the male line until the first female Harley (Elizabeth) in Australia who married James Blackman (1760 - 1842). Elizabeth Harley and James Blackman came out free to Australia. James was first a Police Chief in Bathurst, New South Wales and then a notable Explorer in the Mudgee district of New South Wales.
Of the Cotter generations I can only source 6 Generations from the time the first Cotter was transported to Australia.
The Davison line only goes back 6 Generations in Australia from my generation. After my generation there are three more generations, as I am a great grandmother now.
It seems that once both the Cotters and the Davisons left Ireland and England respectively, there seems to be no secure link existing publicly to their forebears. Davisons came from Essex, England. There are still Davisons that do live in Essex, and I have spoken to them, but they have no knowledge of past relationships. There is a link also to Deptford in London, but it is hard to follow it up without evidence. I haven't found any Davisons there now, even though I went to London, but populations nowadays are so mobile. Also Deptford was a very poor neighbourhood and much of the place has been demolished and rebuilt in the previous two centuries.
In England, the Davisons in the 1700 -1800's were originally farmers in Essex.
As far as I can ascertain, the English Davisons came from Toppesfield, Essex.
Barnes, Rev. H.B., The Register of Baptisms, Marriages and Burials at St. Margaret's, Toppesfield Parish, Essex Co., England, 1659-1660 (Merrill Press, Topsfield, Mass., USA, 1905) I have spoken to a family of Davisons who are farmers, but they were not interested in Genealogy, no doubt too busy on the farm.
It was a common thing in those times, when a family member ran foul of the law and was sent to Australia, that the family seems to have wiped all knowledge of them out of the family history. Pre-Victorian and Victorian times were very much a time of "appearances matter above all else." This happened in Ireland as well.
I was born at Young, New South Wales, Australia in the Mercy Hospital run by the Mercy nuns. 
Unfortunately, Glen Roy Davison, the father of the children could not overcome his alcoholism throughout his life. He was a man with a great sense of humour when sober, who cooked great stews for the kids, but when he drank it was a different story involving neglect of his family. He was often on the wrong side of the law. https://trove.nla.gov.au/newspaper/ articles:      
I spent my first years, from the age of 1-5 in Camperdown Children's Hospital, Sydney. I sustained injuries in a fire when I was 11 months old and had multiple head, body and bone injuries which prevented me from standing up or walking, caused by violent treatment and neglect from both parents due to the curse of alcohol. I spent my 2nd year on a spinal board looking at toys in a box on the floor which the nurses put there for me to see. (All this information is in the nurses' notes which I obtained through Freedom of Information, after 1988- Australia's bi-centenary year.) Trove.com.au articles:    My natural parents had other children to look after, and were finding it difficult to cope with one more, especially one who needed full time care. They moved from New South Wales to South Australia to avoid further prosecution from the Child Welfare Department.
A nursing sister at Camperdown Hospital who had looked after me for 4 years applied to foster me as a daughter, and so I was brought up outside the family from then on until I was 20 years old.
I went to schools in Manly, New South Wales. Worked for some time after leaving school at 16 in a Bank in Manly, (a suburb of Sydney, New South Wales) and then entered a Benedictine convent, Tyburn Priory, which at that time was in Manly near the Manly Hospital and St. Patricks Seminary.  It moved to Riverstone, a suburb of Sydney, in the Parramatta diocese then after 2020 the convent relocated again to a nearby property. When I have visited London, I stayed in the guesthouse of Tyburn Convent, Hyde Park Place near Marble Arch.
What others do to us, is their responsibility, - what we do with our lives is ours!
I always say "Be nice to people because one day you may find you are related to them!"
I will never call myself old, because I was born at Young, and so I am forever a Young girl.)
Having experienced the difficulty of accessing to edit or add informtion to my brother's Geni.com family history account after he died, (even though I was on his "allowed" list) I would like to state that when I die sometime in the future, or after 1.1.2040, whichever comes first, that my wiki family history data will be "unlocked" where it is private, so that it is accessible to any generations following me. Linda Davison-Taylor 15th February, 2020
On my mother's side of the family, through her father Michael Gerald Cotter, the Cotter DNA Project is located at http://www.familytreedna.com/public/sonsofottar and has so far shown that all members have the Norse-Frisian R1b1a2 y-DNA which indicates our Norse origins in south-east Ireland.
Mothers do not have their father's Y-DNA, as females do not have the Y chromosome. Male humans have an X and a Y, but females have two X chromosomes and no Y chromosome (except for some very rare conditions). When you can, always choose folks from the older generation to test.
"Family Myths" that persisted until I started researching documents and sources to prove or disprove them. I began in the Bi-Centenary of Australia (1988) when Freedom of Information was released to everyone.
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