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They married 1951:

19410/1951 SMITH JAMES EWEN STEEL JANET MAY

From NSW BMD http://www.bdm.nsw.gov.au/bdm_fh.html

I am trying to find the Cemtery where James and his family were buried.
I believe it woul dbe back in one of the Sydney Cemeteries and maybe close to Lithgow.
James married Janet May Steele - date unknown
They had three children Kathleen Isobel 1953; Wendy a1956; and Derek 1959.
On their way home to Lithgow NSW, their car skidded and hit a post 8 miles north of Gundagai. All died in teh car crash except Wendy who was travelling behind in a second car. This happened on 1/4/1964.
James was a Dentist of Hassans Walls Road, Lithgow, NSW.
They had been away on an Easter holiday.
They may have been visiting the Smith Family which lived in Melbourne.
James parents are Edwin Arthur George SMITH and Margaret Isabel WELLS.
James was 38 years of age.
I have articles from the TROVE library and other articles of him winning a scholarship to Scotch College in Melbourne years before.
He had another brother Edwin Maxwell SMITH and a sister of unknown name or birth date.
However my main problems are: 1 finding the Cemetery where they are buried; and 2 the marriage date.
If anyone can help open this mystery up it would be great.
Kev :-)