Katzenellenpogen Family Rabbinate
Rabbinical genealogies are of extraordinary importance in Jewish genealogy. Rabbis and their students and followers frequently recorded their own genealogies as prefaces to their religious commentaries. Sometimes these family histories went back many generations. Many Ashkenazi Jews claim to be related in some way to the most prominent Rabbis and their families. Establishing a link to them makes it possible to extend one’s family history very far back in time
Other than the genealogies that Rabbis provided themselves, there have not been many ways to independently verify their accuracy, or point out any errors that may have been made and repeated over many generations. The poll tax (census) lists of the Grand Duchy of Lithuania, during the 1700s, are a valuable source of actual records for Lithuania-Belarus, which provide documentation for genealogies.
This is particularly important for the most famous families, such as the Kazenellenpogens, who dramatically influenced the religious and cultural events of their times, over several centuries and across a wide swath of Europe.
The Chief Rabbi (Av Beth Din or ABD) of Keidaniai, until 1714, was Rabbi (R’) Ezekiel Katzenellenpogen (a descendant through the female line who had adopted the name from the Katzenellenbogen male line.) He then became ABD of the famous triple community of Altona-Hamburg-Wansdbeck where he remained until his death in 1749.
His son R’ David succeeded him in 1714 as ABD Keidaniai, and he was succeeded by his son, R’ Meshullam Zalman ABD Keidaniai.
Up to this point there are no discrepancies in the rabbinic succession. From this point on there is an error, which appears to first be found in Da’at Kedoshim. It states that R’ Meshullam Zalman was succeeded by his older son, R’ Menachem Nachum as ABD Keidaniai (until about 1780) and then Menachem’s son, Moses Mordecai, succeeded him. This information is repeated in Markowitz’s Rabbis of Keidaniai.
Da’at Kedoshim further states that another son of Meshullam
Zalman was Mordecai “who signed in the book Luchot HaEidut,” together with the wise men of Lublin (also brought down in LeKorot HaYehudim BeLublin). These two sources make no mention that he remained in Keidaniai, and certainly not that he was the ABD of Keidaniai.
However, in the 1784 Radziwill-owned town of Keidaniai census the ABD (Rabbi of the Synagogue) is listed as Morkiel (i.e. Mordecai) Zalmanowicz (i.e. son of [Meshullam] Zalman who had by that time succeeded his brother, R’ Menachem Nachum (who, as stated died about 1780). However, there was an interruption in the Katzenellenpogen family’s ABD position since the still extant Keidaniai pinkas of the Chevra Kadisha (burial society), the ABD between the two brothers was R’ Jehiel ben Joseph HaKohen who must have ruled between about 1780-83.
Further, the 1897 epitaph of Pina Gitel, first wife of the famous and prominent R’ David Tebele Katzenellenbogen, ABD St. Petersburg, states she was “daughter of R’ Meshullam Zalman, ABD Joniskis (Yanoshak), son of R. David ABD Wilki, son of R’ Moses Mordecai ABD Keidaniai, son of R’ Meshullam Zalman.”
The conclusion is that Da’at Kedoshim (and thus Markowitz) confused the two Mordecais. Moses Mordecai was in fact son of Meshullam Zalman and not of Menachem Nachum (brother of Zalman). This makes the Mordecai of Lublin fame, son of Menachem Nachum, having no connection to the Keidaniai rabbinate.
Further, the misplaced sons of the Mordecai son of Menachem Nachum actually belong to Moses Mordecai—one being David of Wilki, father of Mordecai, father of Joel Isaac (great-great-great-grandfather of this writer).
Another unpublished source that now also becomes substantiated, thanks to the 1784 census, is a South African pedigree manuscript, dated 1886. It also confirms that it was Moses Mordecai, son of Meshullam Zalman who was the ABD after Menachem Nachum and that Moses Mordecai was the father of David of Wilki.
 This was quite common when a man married into a renowned, learned or wealthy family.
 Eduard Duckesz, Iweh LeMoshav, (Cracow; Josef Fischer Press, 1903), 21-29.
 Israel Tuvia Eisenstadt, Da’at Kedoshim (St. Petersburg; J. Berman & Co., 1897-98), 17-25.
 Moshe Markowitz, Lekorot Ir Keidnaniai ve-rabaneha (Warsaw; Aryey Judah Leib Lipschutz Press, 1913), 6-7.
 Shlomo Baruch Nissenbaum, LeKorot HaYehudim BeLublin (Lublin; Abraham Feder Press, 1900), 100.
 For full details see Neil Rosenstein, The Unbroken Chain (Lakewood, NJ; CIS Publishers, 1990), chapter 8.
Source: Jewish Family History Foundation , 18th century Grand Duchy of Lithuania records.