Georg Cantor from St. Petersburg

Recent archive research allowed us to recover the early biography and history of G.Cantor's family. Three generations of his family lived in St. Petersburg and were closely connected with its culture, science, and trade. What reasons impelled Catherine II, Paul I, and Alexander I to patronize the family? The members of Cantor's family contributed to the creation of St. Petersburg's culture of the XIX century.
Georg Cantor was born in the house that stood on the 11th Line of the Vasilievsky Island and attended a school on the Nevsky avenue. He continued to remember remarkable Petersburg when he lived in Germany, and he dreamed to return to Russia in the end of his life.