I just found a post by Rudy3 with considerable information on the elusive Sukhotin:
Sergej Mikhajlovich Sukhotin (1887-1926)
Prince P. P. Isheev (1889-1959) writes in his memoirs: ”My wife and I lived in a good apartment in a big, new house on B. Pushkarskaja Str ....., in which prince Chagodaev rented one room. The young Chagodaev at that time had just returned from England, he visited as soloist of Andreev’s balalaika orchestra, before the war. On request of the King of England, Andreev let him stay in London, where he teached at the Court, at the Life Guards, and gave private lessons in playing the balalaika. ..
His sister, the well known pianist Irina Eneri, who was married to lieutenant Sukhotin of the Life Guards Infantry (Rifle) Regiment – was a very good friend of princess Yusupov and spent long days with her at her palace. So Sukhotin became befriended with prince Yusupov and took active part in the conspiracy against Rasputin. I heard about all this from Chagodaev, as well as about all the details on the day of the murder. It is generally believed, and written by all, that Purishkevich killed Rasputin. In fact Rasputin was shot and killed by Sukhotin. ...
Irina Eneri, pseudonym for Irina Goryainova-Chegodaeva (1897-1980), performed in concert halls since she was twelve. In 1909 she also performed in Tolstoy’s Yasnaya Polyana. She and Sergej Sukhotin had a daughter called Natasha. However, one year later she left her husband and moved to the west. Nikolaj Gumilev mentions her in one of his poems.
Sukhotin was never punished for his participation in the murder of Rasputin. After the revolution we find him in Yasnaya Polyana. He has been in prison, like Tolstoy’s daughter Alexandra (1884 — 1979), with whom he starts to cherish Tolstoy’s memory in building up the Tolstoy museum.
His stepmother is Tolstoy eldest daughter Tatyana, who is married to Mikhail Sukhotin (1850-1914, 1st marriage with baroness M.M. Bode-Kolycheva).
In 1921 Sukhotin marries Tolstoy’s granddaughter Sophia Andreevna Tolstaja (1900-1957) in Yasnaya Polyana. However, soon after the wedding Sukhotin suffers a stroke (January 1922), that leaves him paralyzed. He divorces from his wife. Their daughter is born after the divorce. He now lives in his wife’s mother’s apartment. His stepmother and an aunt feel pity for him and decide to write to Yusupov in Paris, to ask for help. Yusupov answers: send him here!
With the help of a Czech diplomat Sukhotin leaves for Paris (March 13th, 1925). In Warsaw the diplomat leaves the train for a moment, to discover, when he returns into the wagon, that Sukhotin is gone. The train does not wait and leaves, together with the Czech diplomat. Sukhotin has gone walking into the city. He falls, people think he is drunk, but in the end he is taken to a hospital. After some time he is somewhat better, and leaves for Paris to recover. Shortly after arrival in Paris he dies (1926).
In 1925 Sophia married a second time, famous poet Sergej Yesenin. Her third husband became in 1948 Alexander Timrot.
Alexandra Tolstaya, who was appointed by Lunacharsky as commissar and later caretaker of Yasnaya Polyana, but also was arrested five times, left Russia in 1929 to read lectures about her father in Japan. In 1931 she declared not to return to the Soviet Union. She lived in the United States since 1931. In 1939 the Tolstoy Foundation was founded. Alexandra worked there until the end of her life. http://forum.alexanderpalace.org/index.php?topic=1887.msg496518#new