I assume you are taking the information from an online tree or subscription only website as the year of birth for Doris is earlier than you have stated.
Birth
ANONI Doris Isabel
Father Alex Francis Mother Ethel JEFFRIES
At Armadale 1918 Reg#16195
http://nla.gov.au/nla.news-article1412501The Argus 21 Sep 1918
ANONI. - On the 25th August, at; ''Nerrina" private hospital, Armadale, the wife of Mr. A. F. Anoni, South Yarra - a daughter (Doris Isabel).
Death
RENDALL Doris Isobel
Father ANONI Francis Mother Ethel JEFFRIES
At Prahran 55 years 1974 Reg#2582
Doris's cremation record at Springvale Botanical cemetery
http://smct.org.au/deceasedsearch/result/387872Her death certificate should list both marriages and children from both including their ages at her time of death.You can purchase an image of certificates in Victoria online and immediately download
http://www.bdm.vic.gov.au/home/family+history/You need to view the image of the electoral roll to see the address. Doris was enrolled to vote living in the
Electoral Division of Henty.Australian Electoral Roll
1936, 1937
SELBY Stephen Turner 11 Wilton Grove, Elwood Painter
1943
SELBY Doris Isabel 49 Shelley Street, Elwood Munitions worker
[Only
SELBY to vote at this address]
http://nla.gov.au/nla.news-article1094575The Argus 25 May 1945
MISSING FRIENDS
TO STEPHEN TURNER SELBY, Formerly of 11 Welton Grove, Elwood, a Member of the Australian Imperial Forces. But Now of Parts Unknown.-Take notice that your wife, Doris Isabelle Selby, has instituted proceedings for a divorce on the ground of desertion.
Unless you ENTER an APPEARANCE in the office of the Prothonotary of the Supreme Court of Victoria at Melbourne on or before the 21st day of June, 1945, the case may proceed In your absence.
If you Intend to defend the suit you must file an answer In the said office on or before the 1st day of July, 1945; and further take notice that the sealed copy petition and copy citation in this suit may be inspected at the office of the petitioner's solicitor. HULBERT A. GREENING, 422 Collins street, Melbourne, solicitor for the petitioner._
1949
TRENDALL Doris Isabel 192 Neerim Road, Carnegie HD
1972
TRENDALL Doris Isabel 2/13 Garden Avenue Carnegie HD
TRENDALL George Frederick 2/13 Garden Avenue Carnegie Fitter
George died in 1990
http://prov.vic.gov.au/index_search?searchid=54TRENDALL George Frederick
Retired Woodside Beach 13 Aug 1990
1041/779 VPRS 28/P21, unit 168; VPRS 7591/P17,
George's WW2 Service Summary
http://www.ww2roll.gov.au/Veteran.aspx?serviceId=N&veteranId=1176010http://www.freebmd.org.uk/cgi/search.plBirths Jun 1919
TRENDALL George F Ford Willesden 3a/341
and possible marriage of parents
http://www.freebmd.org.uk/cgi/search.plMarriages Mar 1908
FORD Alice Hendon 3a/381
TRENDALL George Frederick Hendon 3a/381
Australian Electoral Roll
1958 New South Wales
SELBY Stephen Turner 81 Cameron Street Rockdale, Painter
Marriage in NSW
17988/1952
SELBY Stephen Turner
WHITE Iris Edna
District Marrickville
Stephen's WW2 Service summary
http://www.ww2roll.gov.au/Veteran.aspx?serviceId=A&veteranId=440702Cando