Both Rav Moshe Mordechai Epstein, the Rosh Yeshiva in Slabokda and later in Chevron, and his brother in law and Chavrusa in Kollel, Rav Issur Zalman Meltzer, the Rosh Yeshiva in Kletzk and later in Yerushalayim in Eitz Chaim, were both niftar on 10 Kislev although 20 years apart. Much of the post holocaust Yeshiva world in both America and Eretz Yisroel can be traced back to the influence of these two great Geonim and tzaddikim.
Rabbi Isser Zalman Meltzer was born in the city of Mir 5630/1870 At the age of 10 he learned at the Mir Yeshiva. By the age of 14 he went to learn in Volozhin yeshiva under the Netziv and Rav Chaim Soloveitchik, where he remained for seven years. During his engagement period Rav Isser Zalman became gravely ill. He sent a letter to his Kalla suggesting that under the circumstances she could break the Shidduch. His Kalla set out to ask the Chofetz Chaim what to do. The Chofetz Chaim told her that health and long life are not necessarily synonymous. He recommended that they get married and wished them both Arichas Yamim which they had.
After getting married in Kovno he remained there learning with his brother in law Rav Moshe Mordechai until they both were invited to give shiurim in Slabodka. In 1897 the Alter of Slabodka sent Rabbi Issur Zalman to Slutzk to become Rosh Yeshiva of the Yeshiva that Reb Yaakov Dovid Vilovski (Ridbaz) asked the Alter to establish in his town. He took 14 top talmidim of Slabodka with him.
Six years later in 1903 when the Ridbaz” the Rav of Slutzk left to America to raise funds in America for the publication of his famous commentary on the Talmud Yerushalmi and to become Chief Rabbi of Chicago, Rabbi Issur Zalman was appointed as the Rav of Slutzk armed with a hastily telegrammed Semicha from both Rav Chaim Soloveitchik and Rav Yechiel Michel Epstein, the author of Aruch HaShulchan.
At the outbreak of the Bolshevik revolution Rav Isser Zalman and his son in law Rav Aharon Kotler fled Russia to Poland. Rav Aharon stayed in Poland to head the Yeshiva in Kletzk while Rav Isser Zalman emigrated to Eretz Yisroel and was appointed Rosh Yeshiva of Eitz Chaim in Yerushalayim. Rav Isser Zalman is credited with introducing the derech of the Lithuanian Yeshivos to Eretz Yisroel and he was “Rosh Yeshiva” to the “Roshei Yeshivos.”
His Even HaEzel on the Rambam has become a classic in the Yeshiva world. He was Niftar 10th Kislev 5714/1953 at the age of 83 years old.
Rav Moshe Mordechai was born in Bakst in Vilna in 5626/1866. When he was 15 years old word spread around Volozhin about his incredible knowledge of half of Shas. He learned under Rav Chaim Soloveitchik who was Rosh Yeshiva at the time. He was considered an exceptional Ba’al Michadesh. After his marriage in Kovno he learned together with his brother in law Rav Issur Zalman Meltzer under Rav Itzele Blazer the talmid and successor to Rav Yisroel Salanter. Rav Issur Zalman said that at the time he himself knew the whole Avnei Milu’im by heart and that many of the chidushim Rav Moshe Mordechai wrote were identical to that of the Avnei Milu’im.
Before he even turned 30 years old he was invited by the Alter of Slabodka to give Shiurim at the famed Slabodka Yeshiva. Shortly thereafter Rav Moshe Mordechai was appointed Rosh Yeshiva. Rav Moshe Mordechai guided the Yeshiva through some tumultuous times including the breakup of the Yeshiva over the learning of Mussar which Rav Moshe Mordechai and the Alter refused to relinquish despite strong objection. He also guided the Yeshiva through the dispersal and wandering of the Yeshiva during World War I. Rav Moshe Mordechai was so devote to the Yeshiva that he turned down prestigious Rabbinic positions in Kovno and Bialystok to remain in Slabodka. In 1910 after the passing of Rav Shmuel Salant the Rav of Yerushalayim he was offered to succeed him. Despite his dream of moving to Eretz Yisroel he turned it down as well.
In 1924 at age 58 he moved with part of the Yeshiva to Chevron in Eretz Yisroel while leaving behind Rav Eizek Sher as Rosh Yeshiva in Slabodka. The Yeshiva was thriving in Chevron until the tragic 1929 Chevron massacre forced the remains of the Yeshiva to relocate to Yerushalayim. Rav Moshe Mordechai never recovered from the heartbreak of the massacre and the loss of many precious talmidim. He was Niftar in 10 Kislev 5694/1933.
He left behind many talmidim including the postwar architects of Torah in America, Rav Aharon Kotler, Rav Yaakov Kaminetsky, Rav Yitzchok Hutner, and Rav Yaakov Yitzchok Ruderman. Among his son-in-laws were the Roshei Yeshiva of Chevron Yeshiva Rav Yechezkel Sarna and Rav Moshe Chevroni as well as Rav Moshe Finkel the son of the Alter of Slabodka. Rav Moshe Mordechai left behind his permanent imprint on the shifting location of Yeshiva world.
{Revach.net/Matzav.com Newscenter}
You forgot to mention that Rav Aron Kotler was his son-in-law.
They did mention it in the 5th paragraph.