There are no births for a Stephen Martin / mother Crowther he must have been born elsewhere or the memory of the father's name was somehow missconstrued
There is only one birth for a John* in Cranbrook (no mother's name used in search) and Nigel found it, mother Crowther (used * in cas2 Johnathan, Johnathon,etc.)
Only three births all told mother Crowther, Joan in 1925 there was also a Gillian A Martin Sept. Q 1938 / Cranbrook vol.2a p.1833
While there are numerous marriages using the two surnames, there is only one marriage of a "Stephen" Martin to a Crowther and that's the one to Beatrice E. in Ticehurst...she may have used her middle name except on documents which may have been Elizabeth...
Being that you have the date of birth which was used on a passport, it makes sense to send for that birth cert & confirm..as I think you may have the right man and a small price to pay to be sure...No explanation for the Australian family thinking otherwise
~~~
Thought a little harder, and if John adopted his middle name of Hugh, perhaps this person in Australia was a brother also using a middle name of John ( sounds as though a family rift may have kept the sibling's descendants from knowing about each other...) Finding the births in India would be a boon....maybe one might find a Stephen John...
J.J.
Here is a birth for a Beatrice Elizabeth Crowther / Ticehurst / vol. 2b p.116
* Just noted didn't add the year, etc. it was September quarter 1899
