Nidd family - origins of Thomas Nidd?

Grandad's grandfather was Thomas Nidd - please see the separate blog post which is focussed in its entirety to him and his wife Margaret Nidd nee Maher.

I believe he arrived in New Zealand on the ship Rajah around 1857.  Possibly he came via Australia and possibly he  also came with a brother, Robert Nidd.  

Robert Nidd was the only other Nidd in New Zealand at any time who has not been a direct descendant of Thomas.  Robert Nidd married Isabella McCready on 22 June 1863 in Dunedin.  They appear to have lived on the West Coast of New Zealand.  See more about this family here.

But where did these Nidds come from originally?  The following is speculation, but I think that it is probably the right story:

Richard Nidd was born 1787 Holbeach, Lincolnshire.  Richard married Mary Johnson. Mary was born around 1807 in Emneth, Norfolk.  Richard and Mary had six children.

Frederic Nidd born 1827, Norfolk, England

Thomas Nidd born 1832 Norfolk, England possibly christened on 25 January 1832 as William Thomas Richard Nidd at Wisbeach, Cambridgeshire

Robert Nidd born 1834 Norfolk and christened 5 July 1834 Emneth, Norfolk

Richard Nidd born 1836 Norfolk and christened 15 May 1836 Emneth, Norfolk - died in the March quarter of 1843 at Wisbeach, Cambridgeshire aged 7 years

William Nidd born September 1838 Wisbeach, Cambridgeshire

John Henry Nidd born 1841 Wisbeach, Cambridgeshire

Richard Nidd Snr died in the September quarter 1841, leaving Mary Nidd with four small boys; Thomas, Robert, William and John.  In 1845, Mary appears to have had another child - daughter Sarah Ann Nidd - but there is no way Richard could have been the father!  Tellingly, this child was not christened for another ten years. 

If this is the family of Robert and Thomas, and they went to New Zealand/Australia - what became of the rest of the family?

John Henry Nidd married 19 year old Mary Jane Lashbrook in the March quarter of 1869 in East Stonehouse.  They had at least two children, and seem to have lived around Kent and Hampshire.

It is unclear if William Nidd ever married.