You may already have this and it doesn't help with finding William.
Monaro Pioneers site has a photo of the grave of William and Martha's eldest son at Bredbo.
NSW BMDs show his
birthNSW 9178/1868 reg Goulburn
William J H DAVIS, parents William, Martha
Death
NSW 14933/1927, reg Cooma
William DAVIS, parents William, Martha
Monaro Pioneers - you need to register but it's free and often has fairly reliable information (check always though!) The photo shows his death date as 12 July 1927. He seems to be the only DAVIS buried there and there are no other relationships, other than parents shown for him on the Monaro Pioneers site.
http://www.monaropioneers.com/TNG/getperson.php?personID=I286303&tree=MPI have included Monaro Pioneers' references where shown
There is an entry listed for
DAVIS, William GeorgeBirth and death dates unknown
Note: aboriginal
Married Martha ORME, 1 Feb 1869 Collector, NSW ( ref: NSW BMDs)
These are the children listed on this site
1. Davis, William John Henry, b. 12 Mar 1868, "Willeroo", Lake George, NSW
2. Davis, Ada A., b. 1869, Goulburn, NSW
3. Davis, Frances E., b. 1871, Goulburn, NSW
4. Davis, Emily Esther, b. 1873, Goulburn, NSW
5. Davis, Arthur Albert, b. 1875, Goulburn, NSW d. 1951, Wollongong, NSW (Age 76 years)
6. Davis, Martha, b. 1878, Queanbeyan, NSW
7. Davis, Amy Elizabeth, b. 1879, Queanbeyan, NSW d. 1933, Ashfield, NSW (Age 54 years)
8. Davis, Richard Henry, b. 1881, Queanbeyan, NSW d. 1883, Queanbeyan, NSW (Age 2 years)
9. Davis, Victoria, b. 1883, Queanbeyan, NSW
10. Davis, Sydney J., b. 1885, Queanbeyan, NSW d. 1885, Queanbeyan, NSW (Age 0 years)
11. Davis, Edward George, b. 1887, Cooma, NSW
12. Davis, Annie M., b. 1890, Captains Flat, NSW
Monaro Pioneers has this death attributed to William DAVIS, the first-born son
d. 1938, Wollongong, NSW (Age 69 years)
However I would dispute this as the only index entry on NSW BMDs for a death of a William DAVIS in Wollongong in 1938 has the parents listed as William and
Mary. I feel that the Bredbo burial is more likely to be the right one. However it would need checking.
Monaro Pioneers has quite a lot of info re Martha.
Judith