 Marytė married Mečislovas Mackevičius, who would later serve as the minister of justice on the Provisional Government of Lithuania in 1941.Mykolas Sleževičius' brother Kazys Sleževičius was a prominent geophysicist in Lithuania, Head of the Department of
Geophysics and Meteorology at the Lithuanian University (now Vytautas Magnus University), later at the Vilnius University.Sleževičius died on 11 November 1939 in Kaunas.