Have you looked for Emil's obit or death certificate? Either of them may have information re:birthplace or family members.
This looks like Emil Victor with his parents in 1895
Minnesota State Census, 1895
Name Emel Hoberg
Event Place Royalton township, Pine, Minnesota
Age (Original) 16y
Birth Year (Estimated) 1879
Race (Original) W
John Hoberg M 47y Sweden
Carrie Hoberg F 35y Sweden
Emel Hoberg M 16y Sweden
Nels Hoberg M 14y Sweden
John Hoberg M 13y Sweden
Chas Hoberg M 12y Sweden
Christine Hoberg F 10y Sweden
Anna Hoberg F 5y Sweden
Citing this Record
"Minnesota State Census, 1895," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MQDM-LJV
: 2 April 2016), Emel Hoberg in household of John Hoberg, Royalton township, Pine, Minnesota; citing p. 2, line 35, State Library and Records Service, St.Paul; FHL microfilm 565,795.
So, now you can search for records for his siblings to see if they have a birthplace listed- familysearch.org is a good place to start.
You can order his naturalization record here, I am not sure what information is included, I would ask them prior to ordering, in case it is just an index listinghttp://www.ironrangeresearchcenter.org/details/7/429853/
His WWI registration states he is a citizen, as a result of his father's naturalization, while he was still a minor. This means, he may be listed as a child on his father's naturalization records, but not have an application of his own.