Here is what I know about the two cossacks.
Timofej Ksenofontovich Jasjtjik (Yaschik), 1878-1946. Kuban-cossack, and served as cossack to Nicholas II and then MF from 1915-1928.
After MF's death he had a little shop in Copenhagen. He was married to Marfa Sidorska who was killed by the bolschevics in 1921. Jasjtjik keept correspondance with his children who all lived in Russia. He remarried in Denmark, and he also wrote his memoirs.
Kiril Ivanovich Poljakov, 1879-1934, Don-cossack, and served from before 1916(I don't know exactly when he started) until 1928, whereafter he got a job cleaning bottles in a wine-shop . He was married to a russian woman but that is all I know.