Hi again Anthony.
Always best to work backwards from something you definitely know to be true!
So, starting with the death of your father, his death registration gives the following information
Gordon Dumbrell Joy
Birth Date:11 Feb 1916
Date of Registration:Oct 2004
Registration district:Kent
Register Number:KDC3
District and Subdistrict:564/1C
Entry Number:291
Birth dates and ages given at death can be inaccurate as they are dependant on what the person registering the death knows. In this case if we look for a birth registration we find
Births Mar 1916
Joy Gordon D Dumbrel Tonbridge 2a 1517
Dumbrel is the maiden name of the mother. Maiden names of mothers are shown on birth indexes from the September Quarter 1911. Tonbridge is the Registration District, 2a the volume and 1517 the page number. This reference enables the certificate to be located by the GRO. Note that March 1916 relates to births registered in January, February and March 1916.
A good free site for finding birth, marriage and death registrations is
http://www.freebmd.org.ukYou might want to try searching that site for surname Joy and mother's maiden name Dumbrel/ Dumbrel to find some of the siblings of Gordon.
You are right that one of Gordon's brothers died in WW1. Have a look at this entry on another excellent free site
http://www.cwgc.org/find-war-dead/casualty/57562/JOY,%20HARRY%20JAMESWhen you start researching your family it is a good idea to collect together as many pieces of information as possible from family members including birth, marriage and death certificates. Have you subscribed to any family history research sites? Once you are back to 1911 the 10 yearly censuses are excellent for furthering your research.
Finally (for now) I have death dates for William Edwin Joy on 1 March 1936 and for his wife Louisa Kate on 3 January 1944.
Barbara