Val, parish records of christenings don't give that specific info re parents.
Perhaps studying the wills of the Cottiers would help you to specify who is who. It is tedious but often produces good results.
Brian's site lists the Cottier wills which saves you one step of ordering the indexes--there are 2 for each year.
Order the likely candidate's wills and see what you get--don't forget to look for both male and female.
Keep us posted.
Donna