 Mykolas Sleževičius was born on 21 February 1882 in Drembliai village in Kovno Governorate of the Russian Empire (now part of Raseiniai district municipality, Lithuania).He was the oldest of two brothers, with Kazimieras Sleževičius, who would grow up to become a geophysicist, born in 1890.That same year, their father, Feliksas Sleževičius died.