I am the grandson who works at IU to whom Roberta refers in her message. The Mollie (not Molly) Zaretsky who was the sister of Henrietta Zelikow was married to Isaac Zaretsky, who lived in the Borough Park area of Brooklyn.
According to my father, Sol Zaret, Isaac had one brother, Chaim, who also lived in Brooklyn. My father is still living.
As Roberta probably knows, her greatgrandmother and greatgrandfather lived on the second floor and Mollie and Isaac the first floor of the same building (as recorded in the 1920 and 1930 U.S. Census. As a child, I would always visit "Tanta" upstairs when we visited with my grandparents.)
On this WWI and WW2 draft cards, Isaac indicates that he was born in Kiev, in Dec. 1883. The 1930 U.S. Census indicates that he immigrated in 1905 and Mollie in 1906. However, I can find no record of their immigration in immigration recrods. (My father says this may reflect Issac's desertion from the Czar's army--he was evidently not eager to be identified.) Like Henrietta's husband, Israel, Isaac worked in the clothing industry (specifically, shirts).
Hope this is helpful. Does anyone have any additional information about Isaac or Chaim Zaretsky,