The 18th of Kislev is the yahrtzeit of Rebbe Yosef Yitzchok of Avrutsch, son of the Tzemach Tzedek and father of the Rebbetzin Shterna Sarah, wife of the Rebbe Rashab and mother of the Frierdiker Rebbe.
He was the 5th of the Tzemach Tzedek’s sons and was named after Reb Yosef Yitzchok, son in law of Reb Boruch Batlan and uncle of the Alter Rebbe.
Rav Yosef Yitzchok married Chanah, daughter of the Cherkasser Rebbe, Reb Yakov Yisroel Twersky, who was a son of Reb Mottele Chernobler and a son in law of the Mitteler Rebbe. After his wedding he stayed in Cherkass, at the table of his shver.
In 5619/1859, still during the lifetime of the Tzemach Tzedek, he was asked by his shver the Cherkasser to accept on himself to become the Rebbe of Avrutsch, in Vohlyn, Ukraine. Despite the Tzemach Tzedek’s objections he traveled to Avrutsch and became the Rebbe of the Cherkasser chassidim there.
Reb Yosef Yitzchok’s derech was in the way of Chernobel, and not Chabad.
He was known as a great baal mofes, with many people travelling to see him and be blessed by him.
During Tishrei of 5637/1876 he fell ill, and he passed away on the 18th of Kislev and was interred in Avrutsch. He was succeeded by his son Reb Nochem Ber, about whom the Rebbe Rashab said that “he serves Hashem truthfully and with a broken heart.”
The Frierdiker Rebbe was named after his zeide.
Based on Sefer Hazichronos, R’ Boruch Batlan had a daughter, Rochel, who married Reb Shneur Zalman. Together, they had 2 children – Devorah Leah and Boruch.
(Boruch married Rivka and their son was Shneur Zalman, the Alter Rebbe.)
Devorah Leah married Reb Yosef Yitzchok.
This means that the original Yosef Yitzchok (whom Rebbetzin Shterna Sara’s father was named for) was the *grandson-in-law* of R’ Boruch Batlan, not son-in-law.