The images below are from an 1899 genealogy entitled "Foster genealogy : being the record of the posterity of Reginald Foster, an early inhabitant of Ipswich, in New England". I followed the suggestion of my friend to look into the FOSTER family as a way to proceed with the CROSBY research.
In looking at the FOSTERs who lived in the Putnam / Dutchess county areas, I found sisters Thankful and Susanna FOSTER (no dates, no husbands) who were the daughters of Nathaniel FOSTER (1725-1787) and Phebe WING (b. 1726). The names Thankful, Susanna and Phebe intrigued me. I wondered if Thankful FOSTER could have been Phebe's aunt, Thankful COX, if her mother could originally been Susanna instead of Susan and if Phebe CROSBY could have been named for Phebe WING.
I have not found anything yet to prove or disprove this theory.