Hello again
Just taking a step backwards, do you have the marriage of Barbara Steel Irvin & Ralph Brady Simpson?
I had a look on www.freebmd.org.uk but could not see it there. Did it take place before civil registration started in July 1837? That would be a pity as church entries prior to this time do not give the fathers' names, however the names of the witnesses could be helpful.
Added: GENUKI says Ralph Simpson married Barbara Irving 27 March 1836 in Earsdon - hopefully you will be able to find the image in the Bishop's Transcripts on www.familysearch.org.uk if you do not already have this. Note yet another variant (I should have thought of that one given the fame of Henry Irving).
I see Barbara & Ralph have a 2 year old son William in the 1841 census (did he die? as there is a baptism for a later William) which suggests a marriage of around 1838/9 but it could of course have been earlier.
Also, I see Barbara Steel Simpson died in New Zealand in 1891 aged 76. Do you have the death certificate (or rather, the historical print out as this has more information), which according to the Department of Internal Affair's website should have the following information (as well as a great deal else which makes me somewhat green with envy):
After 1875 - Registration of Births and Deaths Act 1875 (dated 12 October 1875)
Name and Surname of father
Name and if known maiden surname of mother
Rank or profession or occupation of father
Where born
How long in New Zealand
Where married
At what age married
https://bdmhistoricalrecords.dia.govt.nz/Home/