The brother might have been Friedrich Wilhelm Rosenbrock who settled in the Chewton/Castlemaine district of Victoria and managed the Imperial Gold Mining Company.
He died on the 19 September 1897. Proof would be to see if they share the same parents as your G Grandfather, John Rosenbrock 1829-1925. I believe John and Barbara, had a son named John Frederick ROSENBROCK in New Zealand (died 1922); there was also a police constable of Bendigo named John Frederick Rosenbrock (died 8 Dec. 1911) whom I think was Friedrich Wilhelm's son. Our FTC member Tonkin may be able to help with the Victorian BDM's for Rosenbrock

hi dizzybelle
you didn't really state what you are looking for but here is a few bits & pieces. There is quite a lot more on Papers Past
NOTE All this was a rather quick research so please treat with caution until verified

John ROSENBROCK (1833-1925) married Barbara PEAR (1846-1894 from Dublin) on 1 Feb 1868 in First Church Dunedin. Barbara signed her name with an x
Seven children found but not verified.
There could be others ...
* 1867 - 1896 Agnes Rosenbrock
- married Chow Chie in 1885
* 1871 - 1922 John jnr Rosenbrock
- married Christina Brydon Beattie in 1891. they had 4 children. One son, Fred James Rosenbrock (1905-1944), #535105 was killed in action in Italy).
Three years after John's death Christina married his brother John 'Frederick' Rosenbrock (see *1881)
* 1871 - 1965 Catherine Rosenbrock
- married Emil Albert Ludwig Hennig (1860-1936) of Germany in Dunedin 1892
* 1875 - 1941 Henry Rosenbrock
- married Ann Elizabeth Griffin in 1897
* 1877 - 1932 George Edward Rosenbrock
- married Cora Winifred McKenzie in 1926
* 1878 - 1901 Barbara Louisa Rosenbrock
- married George Forsyth in 1900
* 1881 - 1963 John Frederick Rosenbrock
- married Christina Brydon Rosenbrock in 1925 (nee Beattie 1872-1956), widow of his brother John Rosenbrock jnr
* John Frederick served as Private 23613 in WWI with the 13th Otago Infantry battalion, D Company. He was then a waterside worker & listed his father John of 17 Grosvenor St, Kensington, Dunedin as next of kin. He embarked from Wellington in 1916. He was badly wounded and in hospital in June 1916 and again in Feb 1917. He was discharged in Dec 1919 and died 22 Oct 1963. He is buried at Soldiers Interment, Anderson Bay cemetery with the ashes of stepdaughter, Rebecca Jessie Rosenbrock (1899-1985). Wife Christina is buried at Andersons Bay with 1 of her sons (with John jnr), George Cecil (1904-1935)
* 1883 - 1962 Frederick Charles Rosenbrock
- Frederick served in the Boer war as #5962 with the South Island G Squadron, eighth contingent, departing 8 Feb 1902. His father, as next of kin, was in South Dunedin

in July 1863
there was a J. Rosenbrock from Lyttelton mentioned in the List of Unclaimed Letters

In Dec 1880
a John Rosenbrock received a Forbury School Second-class certificate (Otago)

In Dec 1882
John Rosenbrock & Benjamin Thomas Spinks were charged with stealing two tins of kerosene in Dunedin

In June 1888
Brother J. Rosenbrock was appointed Warden of the Loyal Dunedin Albion Lodge, M.U.I.O.O.F.

In Oct 1889
a George Rosenbrock, aged 15, with a group of other young lads, was charged in the Dunedin Police Court for unlawfully using threatening behaviour in the main street, Kensington and in South Dunedin
(George was often in the courts)

In Feb 1892
a J. Rosenbrock's tender to paint the columns of the telescope gas-holder was accepted by the Gas Committee

In Dec 1892
F. Rosenbrock was attending Forbury School, Dunedin. He was in Standard IV

In Aug 1895
Barbara died aged 48. They were then living in Argyle street, South Dunedin
She is buried in Southern Cemetery with:
* 1901 - daughter Barbara Louisa (aged 22, Mrs George Forsyth)
* 1907 - grandson Albert Louis Rosenbrock (aged 6 months, son of George Edward)
* 1922 - son John Rosenbrock (aged 51)
* 1925 - husband John Rosenbrock (aged 92)
* 1941 - son Henry (aged 66)
* 1958 - daughter-in-law Ann Elizabeth Rosenbrock (aged 84 nee Griffin, wife of son Henry)

Lots of great stuff in here.....Thank you both for the info....

Hi I am also a descendant of John Rosenbrock. My great great grandmother was his daughter Agnes, who married Chinese goldminer Chow Chie. Barbara, John's wife, had two sisters: Mary Jane and Ruth. Mary Jane married Spinks (who is mentioned in the post above).

Wonpat... I had heard about Agnes.... She is buried about 30 k from where I live .....She is .I think the interesting one in the family.. I would love to chat with you about her ..Any ideas how. ?

Barbara Louisa Forsyth (nee Rosenbrock) is my great grandmother. She had a daughter Dorothea Peare Forsyth born 25th March 1901 Portobello who is my grandmother.

I've been doing research on 1st born Agnes Rosenbrock and thus far cannot trace her 3rd daughter Barbara Louisa Chie born 1886 further. Any help appreciated. BTW, Agnes' gravestone in Lawrence cemetery (Find A Grave) is still in lovely condition. Do we assume the family lived in the Lawrence Chinese Camp?

Additional tidbit re Agnes Rosenbrock married Chow Chie 1885, since my post above, I bought marriage certificate to secure his age. For anyone coming at this couple, Chow Chie was 44 when he married Agnes in 1885 (she 18, correct) per the marriage cert and yes the couple both listed their residence as the Chinese Camp at Tuapeka Flat. Marriage was in May 1885, so Agnes was also pregnant with her 2nd child at the time, born later in 1885. I still have no idea re his resting place, so any ideas still appreciated there.

Barbara Louisa Chie is mentioned in WikiTree. Appears a Jeff Thomas has submitted the info. Chow Chie is mentioned as Ah Chie. Have you looked to see if his remains were not removed and transported back to China by boat which did not make it as the boat sunk off the west coast of northland. Would like to know more about Barbara Pear & her sisters Mary Jane & Ruth. Do you know what ship they came to NZ on ?