I can only give you information about his descendants via his adopted daughter Vera:
Vera Naryshkin-Witte was the daughter of a certain Mr. Lissanevitch and his wife, Matilda Ivanovna Nourok, who remarried in 1892 to count Serguei Youlievitch Witte who legally adopted Matilda's daughter Vera from her fist marriage.
Vera Witte married Kyrill Vassilievitch Naryshkin - she was his first wife; he got married a second time, in 1921, to Geneviève van Brouwer.
Vera Naryshkin-Witte and Kyrill Vassilievitch Naryshkin had two children: Lev Kyrillovitch Naryshkin, born in 1905, and Irina Kyrillovna Naryshkina, born in 1912.
Lev Kyrillovitch Naryshkin married twice - first to Edith Jaunez (the daughter of a French minister posted in Oslo) in 1921 (according to Ikonnikov's Naryshkin genealogy), which marriage ended in divorce; and a second time to a certain Marguerite Heller. Lev Kyrillovitch had one daughter, Natalia Lvovna Naryshkina, born in 1929 - I don't know if she was born from his first or from his second marriage. I have no information as to what became of her, if she is still alive, if she ever got married and had children, or not.
Irina Kyrillovna Naryshkina married twice - first to Baron Pallandt, secretary to the Dutch Mission in Berlin, in 1931; her second marriage was to the duke Luigi, son of Thomas Dusmet de Smours, duke in Naples. I have no information as to whether Irina Kyrillovna Naryshkina had any children by either or both of her husbands.