There are often different spellings for the same name - there are not necessarily wrong, just different. If the person could not read, when their name was being recorded, they could not say - that is not how we usually write it - so it would not be corrected to the 'normal' way. What is normally 'Cook' for one person could become 'Cooke' for the same person over different times. Their children could use either or stick to one of them.