I went through my Olden notes and I may have a lead (or more likely a mis-lead!) for you.
William OLDEN and Elizabeth GILES had 3 sons.You already know that their eldest, John, married Mary BREARLEY.My initial research led me to believe that of their other two sons, William only had daughters, and Thomas never married.So I concentrated on John & Mary, and - in fact - they are my ancestors.Most of my notes are on their lines.
HOWEVER ... I have a penciled note on one of my pages that says: "Per Mel Gapen (ancestry.com), Thomas DID marry about 1728 and had a son about 1730.No names,though!That son married someone and had Mary Olden b. 30 September 1757 who married a Mr. Cain and had many children."