East Trentham is south west of Kyneton.  Have a search on google maps.
Some speculative research but this is the only 
O'BRIEN who are farmers in the area but this is in 1903 the first roll after Federation and following the visit of Catherine.
Australian Electoral Roll
1903  Corinella/East Trentham
O’BRIEN Timothy Snr  Farmer  East Trentham 
O’BRIEN Timothy Jnr  Farmer  East Trentham
Marriage
OBRIEN Timothy born Clare
HAYES Margaret born Clare
1868  Reg#4055
Births 
Twins -
OBRIEN Thomas
Father Timothy Mother Margaret HAYES
At Tylden  1869  Reg#25554
OBRIEN Michael
Father Timothy  Mother Margaret HAYES
At Tylden  1869  Reg#25555
OBRIEN Ellen
Father Timothy  Mother: Margaret HAYES
AT Tylden  1871  Reg#12843
OBRIEN Margaret
Father: Timothy   Mother Margaret HAYES
At East Trentham  1873  Reg#13308
OBRIEN Timothy
Father Timothy  Mother Margaret HAYES
At Trentham  1878  Reg#19690 
OBRIEN Anna Maria
Father Timothy  Mother Margaret HAYES
At Trentham  1880  Reg#25684
OBRIEN Bridget
Father Timothy  Mother Margaret HAYES
At Trentham  1883  Reg#13086
OBRIEN Thomas Joseph
Father Timothy  Mother Margaret HAYES 
At Trentham  1886  Reg#25764
OBRIEN Sarah Theresa
Father Timothy  Mother Margaret HAYES
At Trentham  1886  Reg#25765
http://www.australiancemeteries.com/vic/hepburn/tyldenoz_data.htmLots of excellent information on the 
O'BRIEN family of East Trentham.
Interred in the Tylden Cemetery
O’BRIEN Timothy  68 years  24 Apr 1909
Residence East Trentham
Rank  Farmer
Father  Michael O’BRIEN
Mother  Ellen McNAMARA
Death 
OBRIEN Timothy
Father  Michael  Mother Elle McNAMARA
At Trentham East   68 years  1909  Reg#4815 
Probate file on
http://prov.vic.gov.au/index_search?searchid=54Interesting that a photo of the Trentham area is attached to Timothy's Will which was dated 18 Apr 1909 five days before his death.
Interred in the Tylden Cemetery
O’BRIEN  Margaret   80 years  30 Jun 1914
Residence Sunbury
Rank Farmer’s wife
Parents unknown
Death
OBRIEN Margaret
Parents unknown
At Sunbury  80 years  1914  Reg#7632
Deaths at Sunbury are often at the Sunbury Asylum and inquests were routine for deaths in public institutions.
http://en.wikipedia.org/wiki/Sunbury_AsylumInquest Index
OBRIEN Margaret
1914  Ref#549 
Cause Rupture Heart
29 Jun 1914 
http://www.rootschat.com/links/0trt/The Argus  Wed 11 Feb 1903
KYNETON On Tuesday morning, at St Mary's Roman Catholic Church, Kyneton the sacred offices of profession and reception of two nuns were performed. ……... Miss Annie O'Brien daughter of Mr. Timothy O'Brien, East Trentham, received the white veil, and will be known in religion as Sister Mary Teresa. ……..
http://www.rootschat.com/links/0tru/The Argus  29 May 1909
O'BRIEN–LENIHAN.–On the 21st April at St Francis R C Church, Melbourne, by the Rev Father Harnett, of Lancefield, Timothy J, second son of the late Timothy O'Brien, East Trentham, to Bridget Cecelia, second youngest daughter of John Lenihan, Lancefield.
Have a search on 
http://trove.nla.gov.au/newspaper as there may be more about the 
O'BRIEN family from East Trentham and Kyneton.
There is an 
O'BRIEN listing at Trentham East 
http://www.whitepages.com.au/wp/initResSearch.doI do hope this is your family  
  Cheers  

Cando