Although the
Henkikirjat may be the closest equivalent to census records in Finland, they certainly are not the most helpful resource for genealogists in Finland as they do not contain that many details and only include numbers of children in families, not their names.
The church records usually contain far more information and are invaluable sources. In the case of Kähkönens, you should check the archives of the parish of Paltamo.
Paltamo, Communion book 1880-1890:
http://www.sukuhistoria.fi/sshy/sivut/j ... 2&pnum=395
Paltamo, Book of children 1861-1890:
http://www.sukuhistoria.fi/sshy/sivut/j ... 4&pnum=241
Paltamo, Communion book 1891-1900:
http://www.sukuhistoria.fi/sshy/sivut/j ... 73&pnum=17
Paltamo, Book of children 1891-1900:
http://www.sukuhistoria.fi/sshy/sivut/j ... 715&pnum=8
Unfortunately, only members of FFHA can access the links.
The books show the Kähkönen family living in a
mäkitupa called Uusitalo. A
mäkitupa was a dwelling on a small piece of rented land. Until 1890 Uusitalo is listed as being part of farm 37, Pitkäaho, in the hamlet Mieslahti, and from 1891 it is listed under farm 6, Karhu, in the hamlet Härmänmäki. I don't really know the reason for this change, you would have to ask someone more familiar with the parish.
Both Jafet and Eeva were alive in 1900. If you want the dates of their deaths, your best bet would be to contact the Paltamo congregation office.
Jafet's birthdate matches in the one you have, but Eeva's does not, so I traced her backwards. The following are links to older books which can be accessed by anyone.
Paltamo, Communion book 1868-1879:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 43/445.htm is the earliest record in which Jafet and Eeva are together
Paltamo, Communion book 1868-1879:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 43/211.htm
Paltamo, Communion book 1868-1879:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 43/372.htm
These are records from Eeva's time as an unmarried worker.
Paltamo, Communion book 1868-1879:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 43/233.htm
Paltamo, Communion book 1858-1867:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 85/203.htm
Paltamo, Communion book 1851-1857:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 184/64.htm
Paltamo, Communion book 1842-1850:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 184/57.htm
Puolanka, Communion book 1842-1850:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 171/11.htm
These records show Eeva in the Leinonen family.
Puolanka, Births 1825-1848:
http://www.sukuhistoria.fi/sshy/kirjat/ ... 172/69.htm
The Eeva Leinonen who was born in Paltamo in 1852 just happens to share a name. Jafet's wife was born in Puolanka on 1844-12-30 and baptized on 1845-01-26. When she was first entered in the communion book these two dates were mixed up, and for the rest of her life she was listed as being born on 1844-01-26.