Hi Jeanne
I assume your information is from the IGI or from the parish records for Claverly. Your time frames are getting to the stage where you are reaching the limits of parish records, although I notice from the IGI the birth records for Claverly are given as starting 1568. If you look into the batch containing your William, there appear to be a number of siblings for William.
I would suggest that you access the parish records for Claverly & you may be able to find more information (a marriage perhaps for the parents of John). There is an Edward christened 1675 in the same batch, with parents given as John and Margaret. It does happen that a new vicar in some parishes recorded information differently, sometimes giving both parents, sometimes not. Listing all of the family members from the parish at this time & looking at births and marriages may help to break them into family groups. The full copy of the parish register would probably give some burials as well to assist your research.
If you cannot directly access the register, you should be able to order the film of same at your local LDS centre.
Hope this helps
Trish
Edit: Just checked where you are living - If you go to the family search home page
http://www.familysearch.org/Eng/default.aspyou can check if there is a Family history centre near where are