Hi,

I think ellisislandrecords.org only goes as far back as 1892
then there is http://www.castlegarden.org/ which goes back to 1820-1913

You could contact the state archives for Värmland and ask if they know: http://tinyurl.com/avpjmkk

I had a look and found information about both Mattis and Brittas death here:
Glava AI:21 (1886-1890) Bild 374 / sid 361 (AID: v11280.b374.s361, NAD: SE/VA/13154)

Mattis Jansson, b. 14 DEC 1806 in Glava, Värmlands län, Värmland. Died 14 JUL 1889.
Britta Eriksdotter, b. 19 DEC 1811 in Glava, Värmlands län, Värmland. Died 11 JAN 1887.

NB. That page also contains information about Säths and Jans wifes and children.

I had a look for and found Mattis probate here:
Gillbergs häradsrätt FII:29 (1887-1890) Bild 668 / sid 1331 (AID: v47654.b668.s1331, NAD: SE/VA/11147)
I was hoping that it would state the last name of Nils and also the whereabouts of the 3 siblings in the US but all it says is that they are at a known place in the US. Its all witnessed by their sibling Jan, who must have had their addresses.