Thanks Robin. The Chamberling spelling crops up a fair amount in Mass. during the 18th century - that's my impression, without having researched the matter in any detail. I've put up profiles of a family that evidently used this spelling - and which includes two Josephs.
A larger issue related to the recurrence of similar names & close birth dates in different lines, appears to be inconsistent trees across different secondary sources. (For example, one Ancestry.com tree cited a primary source for a Joseph C. with a set of parents outside of that tree.) Seems like much work to be done!
In the meantime, I added several Chamberlains to the Mass. subcategory of the name study.