According to my grandfather Reb Mayer Yacov Schwartz Z"L (son of R' Moshe son of Reb Yitzchoc Eizik), Yenta was the second wife of Reb Yitzchok Eizik. And their son R' Moshe was a "בן זקונים" (youngest child of Yitzchok Eizik & Yenta). Which explains how some children of R' Moshe, are still alive with us today in 2018.
However in the Fekete family, I've noticed that there are more generations between today and R' Yitzchok Eizik. Which makes me wonder if R' Zvi (Hersh) was the son of Yenta, or perhaps the the son of R' Yitzchok Eizik's first wife?
