Send a message to the person who requested a photo of the grave monument of William Peirson with the following comment:
This is William Pearson who is the father to WM Pierson who lived in New York and who is the father of my great grandpa Charles Manly Pearson who married Jessie Muir my great Grandmother. This is the first real true hint that I can actually say is the right lineage because there are so many Pierson's!