in russia, the nuclearization of the family *began* in the second half of the nineteenth century (journals.sagepub.com/doi/abs/10.117…). in (core) england, the process was *finished* by the late fourteenth/early fifteenth centuries (academic.oup.com/past/article/1…). 
in japan, the shift from extended to nuclear families occurred between ca. 1600 and the late-1800s. see The Agrarian Origins of Modern Japan (books.google.com/books?id=YORxu…). below quote from A Companion to Japanese History (books.google.com/books?id=KC2T9…):
from The Agrarian Origins of Modern Japan (pub'd in 1959):
"...taking the country as a whole [changes to agricultural practices in Japan] fell mainly in the Tokugawa period, and their central feature was a shift from cooperative to individual farming."
"...taking the country as a whole [changes to agricultural practices in Japan] fell mainly in the Tokugawa period, and their central feature was a shift from cooperative to individual farming."
shift from kinship-based cooperative farming to an agricultural system founded on nuclear (stem?) families in japan during the tokugawa period (1603–1867). this is ca. 600-1000 years later than the similar change that happened in nw europe.
this shift first started in the kinai region (orange area on map - en.wikipedia.org/wiki/Kinai). osaka's in this region. core japan?
diffs btwn agricultural practices in kinai vs. the rest of japan, esp. towards the beginning of the tokugawa period: kinai had a sort-of manor system (tenancies of nuclear families), rest of japan had kin-based system. the kinai system eventually spread elsewhere.
