Rabbi Menachem Nochum Schneersohn, the Mitteler Rebbe’s son passed away in 1876, at roughly 88 years of age. (Hielman in Beis Rebbe, Vol. II, Ch. 10, writes that Reb Nochum lived in Niezhin for about 50 years. If our assumption is correct, he stayed in Niezhin from his father’s passing in 1828 to his death in 1876, which is 48 years. In the Rebbe’s Reshimos Yuman, 304, it states that Reb Nochum passed away in 1876.) He is buried outside of his father’s ohel in Niezhin, though the exact location of his grave is unknown.