Hi Kate,
... The letter also states that William and Sarah had 6 children in 1859 (when the letter was penned by Jane) but William and Sarah are recorded as being married in Mar 1855. I can find no documentation myself on the Victorian BMD website of their marriage or their children. ...
It seems that you will probably do best by further searching of the Victorian BMDs and by purchasing some certificates.
Some children of William LITTLE & Sarah Jane GORDON:
*James or(?) James Edward 1856 Kyneton - there are two entries in 1856, #13547 (James Edward) and #5743 (James); not sure if these are two separate births ...
*John Gordon 1857 " - #11615
*Mary Jane 1859 " - #15127
*William 1861 Malmsbury - #22163
*Ann Elizabeth 1863 Gree. - #21458
*Sarah 1865 Malmsbury - #16568
*Margaret Louisa 1867 Malmsbury - #9225
*Emma Alice 1868 Malmsbury - #17529
Sarah Jane's death:
*Sarah Jane LITTLE (35) born DERR (presumably Derry), parents Gordon Edward & Mary, died 1869
Victorian death certificates are very informative. The certificate should say when and where William & Sarah Jane married, how long she had been in Victoria, names and ages of children, etc ...
Jane (BOYD) LITTLE:
LITTLE John & LITTLE Agnes b 1846, parents James LITTLE & Jane BOYD, Geelong (this is just a church record)
LITTLE Jane (81) died at Kyneton in 1881, parents Boyd Jno & Elizabeth
That death cert would probably be worth getting.
Certificates can be downloaded immediately from the Vic BDM site.
Good luck,
JAP