There are two different Yavner lines on this forum, one descended from David Yavner and his sister Fruma (1860-1840), from Lithuania, the other from the five sons of Mosemendel Yavner, of Schveksna, son of Mortsche Ytzak Yavner (fl. c. 1850) of Wilno area, Lithuania.
Presumably the two lines are at least distantly related.
I never heard of any relatives from Boston.There was a vague statement that the NYC/CT/VA Yavners (my family) were visited by Yavner cousins from Montreal sometime.Possibly that was the Boston Yavners, or. . . there is another family in Canada.