Tom Dobson & Annie Kirby - question over her father!!!!

As I need to tie up some loose ends with my family tree so I can make a start on my book I decided to purchase the marriage certificate for my great grandparents. From the Mormon website I had gleaned the information that Annie's father was named James but all the Census returns I can find for the family give his name as John!!!! To be sure the information on the Mormon website was correct I needed to see the actual marriage certificate - oh dear - now I don't know what his name was!!!!!! Also the only marriage I can find for a Mary Ann to a Kirby is one to a John Kirby - no trace at all of a James!!!! I'm 99.9% sure that the family on the Census returns are the correct ones as Annie appears with them. I now assume that perhaps Annie didn't even know her father's name as she was only 2 years old when he died - why her mother didn't give her the correct name of John I don't know. I've discovered her oldest sister Jane died at the age of 18, her brother Thomas Hugh didn't marry until he was 50, her sister Alice Ann was 53 when she married - so I don't believe any of them had children except for Annie (my great grandmother). Tom Dobson and Annie Kirby married on August 21st 1887 in the Parish Church at Pickering, North Yorkshire, they were both 20 when they married - her father died in 1869 when Annie was 2 and her mother died in 1910. I think perhaps now I should purchase Annie's birth certificate to check out both parents' names!!!!! Instead of solving mysteries I've created more!!!!