About him from Chabad.org:
R’ Yisrael Aryeh Leib, brother of Rabbi Menachem M. Schneerson, the Lubavitcher Rebbe, was the youngest of Rabbi Levi Yitzchak and Chana Schneerson’s three sons.
Born in Nikolayev in 1909, he quickly became renowned as a scholar of exceptional genius. At a young age, Yisrael Aryeh Leib was already teaching Tanya, the mystical foundational work of Chabad Chassidism, to an audience of eager adults.
He eventually immigrated to Israel, and in his later years he moved to Liverpool, England, to study in the local university. It was there that he passed away in 1952.
Rabbi Yisrael Aryeh Leib is interred in Safed, Israel.