Hi Mavis,
It always helps RootsChatters to help you if you indicate where you obtained the information you say you have. Do you have George's death cert? What else do you know about George? How do you know his middle name? How do you know that he married a Mary Ann COLLIER, that this was ca 1864 in NSW, and that she was born ca 1840 in England

The NSW BDM indexes can be searched online free at:
http://www.bdm.nsw.gov.au/There is a record of a George GODWIN death (no middle initial) at Hillgrove in 1897, parents unknown.
The only marriage of a George GODWIN to a Mary A(nn) between 1788 and 1897 is George GODWIN to Mary A JONES in 1852.
There are no marriages of a Mary COLLIER in that period.
GODWIN children born to parents George & Mary between 1788 and 1906 (Mary A marked with a #; Mary Ann marked with a *) are:
1854 Thomas H #
1857 Elizabeth E (Gosford) #
1859 Mary A (Gosford) #
1861 George P (Gosford)#
1863 Harriet C (Port Stephens) #
1865 John R (Port Stephens) #
1867 Matthew M (Port Stephens) #
1869 Luke J (Port Stephens) #
1870 Charles E (Patricks Plain) *
1873 Emma Florence (Port Stephens) *
1875 Eliza (Inverell) *
1875 Lillias Jane (Port Stephens) *
1877 Hannah Maria (Port Stephens) *
1883 Emily G (Wingham)#
Only 8 Mary GODWIN deaths in the whole searchable period including:
1889, GODWIN Mary A, parents Luke J & Mercy, at Stroud
Regards,
JAP