There are numerous on-line family trees stating our Charles was born in July 1838 to parents John Gear (a butcher) & Mary Ann Manwaring who married on 18 October 1835 at Old Church, St Pancras (London).
HOWEVER: John & Mary were not born in London/Middlesex, as proven in census records, and their only son named Charles, born in July 1838, was buried at St Martin in the Fields on 14 June 1840, aged 1 year 11 months. Family's abode was given as Hertford Street, which matches census records. It explains why he never showed in any censuses and also confirms this was not our Charles. However, it's always possible their son John was actually our John Charles. Perhaps he took his dead brother's name as a "keepsake". Who knows?

I've found no record of Charles Gear coming to New Zealand but did find a possible immigration to Australia from England: Charles GEAR, a single 22 year-old labourer and unassisted immigrant (b. ca 1845) sailed to Melbourne, Victoria, Australia in June 1867 aboard the 'Sussex' which had left from Gravesend, London. Our Charles in New Zealand consistently gave his year of birth as circa 1845.
No New Zealand records are found for Charles before 1870, when he was living on Rochford Terrace in Westport (Buller).

When Charles married Sophia in 1873 he gave his age as 27 which would make his year of birth 1845-46; his occupation was miner. Sophia was only 15 years old; her mother gave her age as 16. Charles was recorded as John Charles on the Intention to Marry document and signed as John Charles on the marriage certificate. The Intention to Marry document also stated Charles had been resident in Westport for five years, which points to him arriving in New Zealand in or before 1868.
In 1873 Charles showed as being on the Miners' Committee for the "Committee of the Northern Terraces for securing the re-election of his Honour Oswald Curtis, for the Superintendency of the Province of Nelson" ('Westport Times', 2 December 1873).
In 1875 Charles and a gentleman named John McKinley successfully applied for the re-registration of store dam at Hatter's Terrace ('Westport Times', 19 February 1875).
Two months later both men successfully applied for extended claim of double ground at Hatter's Terrace, at the old Ruby Lead, on abandoned ground ('Westport Times', 2 April 1875).

New Zealand BDM indexes record Charles's name on his children's birth registrations as Charles John Gear in all cases bar one, where it is just Charles. On the 1887 birth registration of his son Edward Henry, Charles stated he was born in London, England and was aged 42, once again pointing to a birth year of circa 1846.
On the birth of their first child in 1875, Charles gave his address as 'Redmanbar'. Redman's Bar is mentioned in several old newspapers and appears to have been a gold mining claim on the Lyell Creek near Little Ohika in Westport (their second son had the middle name of 'Ohika'). Allegedly Charles made his money in gold mining. If Charles was still a miner there in March 1876 he might have been one of the eight men that tried unsuccessfully to save trapped miner Edward Woodward after a tunnel collapse.
Charles worked as a brewer for one of the local Westport breweries; it's probable he began working at Nahr's Brewery after his marriage.
Charles died two weeks after Sophia. In his will of 1903 he appointed as executor his son Thomas George Gear. He left everything (estate & effects stated to be less than £800) to Thomas, including contents of a life policy, upon trust to use -- the same for the maintenance of his wife Sophia -- during her widowhood and for the maintenance of any of his children aged under 12 years. His free-hold section in Westport was not to be sold unless Thomas was forced to do so to carry out the above instructions.
In 1912 his estate was finally certified by the Commissioner of Stamps during May at Hokitika: Charles Gear £454 ('Grey River Argus', 13 June 1912).

[No New Zealand records are found for Charles before 1870, when he was living on Rochford Terrace in Westport (Buller). As with our ancestor Samuel Lintern, I've found no record of Charles Gear coming to New Zealand but did find a likely immigration to Australia from England -- Charles Gear, a single 22 year-old labourer and unassisted immigrant (b. ca 1845) sailed to Melbourne, Victoria, Australia in June 1867 aboard the 'Sussex' which had left from Gravesend, London.
Charles's son Thomas claimed the Gears came from St Pancras in London, England and had been in county Middlesex/London for generations; he also said Charles's father had been a porter]