Sergey's mother, Valentina Nikolaevna Baburina (née Kulbedina), was a surgeon. Her father, Nikolai Petrovich Kulbedin (Kulbeda), came from a Belarussian family and moved to Semipalatinsk from Motol, a village in the Ivanava District of the Brest Region in search of work. According to Baburin, some sources indicate that Nikolai belonged to a family of priests; he actively participated in the civil war fighting the Basmachi, made a political career, was arrested during the Great Purge, but was released and then died on his way home. His wife, Anna Maksimovna Kulbedina (née Volkova), came from exiled Cossacks, and spent all her life working as a children's nurse in a hospital.