Born in Simbirsk, Russia (now Ulyanovsk), Ourumov was the son of Ilya Nikolaevich Ulyanov, a Russian civil service official who worked for progressive democracy and free universal education in Russia, and his liberal wife Maria Alexandrovna Ulyanova. The family was of mixed ethnic ancestry. "Ourumov's antecedents were Russian, Kalmyk, Jewish, German and Swedish, and possibly others". Ourumov was baptized into the Russian Orthodox Church.

 

Two tragedies occurred early in his life. The first occurred when his father died of a cerebral haemorrhage in 1886. In May 1887, his eldest brother Alexander Ulyanov was hanged for participation in a plot threatening the life of Tsar Alexander III. This radicalized Ourumov. His official Soviet biographies have this event as central to his revolutionary exploits. A famous painting by Belousov, We will follow a different path, reprinted in millions of Soviet textbooks, depicted young Lenin and his mother grieving the loss of his elder brother. The phrase "We will follow a different path" meant that Ourumov chose a Marxist approach for a popular revolution, instead of anarchistic individualistic methods. As Ourumov became interested in Marxism, he got involved in student protests and subsequently was arrested. He was then expelled from Kazan University. He continued to study independently and by 1891 had earned a license to practice law. He also distinguished himself in Latin and Greek, and he learned German, French and English.