Leo’s Hebrew name is Yehuda Leib. It is not known if he was named after someone in the family as per Jewish tradition.
Leo probably had a heart condition all or most of his life. Aaron Rosenberg’s research says Leo died of Rheumatic Fever but the death record says he had Aortic and Mitral Insufficiency for 1 year prior to his death and Ulceratic Endocarditis for 4 weeks prior to his death.
Leo died at 10 years old after a 2 week hospital stay in Massachusetts General Hospital in May of 1903. (May 2-19, 1903)
Leo was buried at Austria Hungry Cemetery in Boston, Massachusetts
"Massachusetts Births and Christenings, 1639-1915", database, FamilySearch (https://familysearch.org/ark:/61903/1:1:F4NL-YMB : 15 January 2020), Leo Rosenberg, 1893.
"Massachusetts Births and Christenings, 1639-1915", database, FamilySearch (https://familysearch.org/ark:/61903/1:1:F4VZ-HHD : 15 January 2020), Leo Rosenberg, 1893.
"Massachusetts Births and Christenings, 1639-1915", database, FamilySearch (https://familysearch.org/ark:/61903/1:1:F4F4-LG3 : 15 January 2020), Leo Rosenberg, 1893.
"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M9TT-S3D : accessed 18 August 2020), Leo Rosenberg in household of Joseph Rosenberg, Precinct 4 Boston city Ward 8, Suffolk, Massachusetts, United States; citing enumeration district (ED) 1265, sheet 13B, family 241, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,679.
Find A Grave: Memorial #131426221 Jewish Benevolent Cemetery, West Roxbury, Massachusetts
"Massachusetts Deaths and Burials, 1795-1910", database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FH4D-Y2G : 17 January 2020), Joseph Rosenberg in entry for Leo Rosenberg, 1903.
"Massachusetts Deaths, 1841-1915," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:NW6B-J1M : 6 April 2020), Leo Rosenberg, 19 May 1903; citing Boston, Massachusetts, v 541 cn 4476, State Archives, Boston; FHL microfilm 2,057,764.
"Massachusetts Deaths and Burials, 1795-1910", database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FH4D-Y2L : 17 January 2020), Leo Rosenberg, 1903.