The subsidiary lines (called "Gorenshi") of the Mito family were the Takamatsu Matsudaira family of Takamatsu Domain in Sanuki Province, the Moriyama Matsudaira family of Moriyama Domain in Mutsu Province, the Fuchu Matsudaira family of Hitachifuchu Domain in Hitachi Province, and the Shishido Matsudaira family of Shishido Domain in Hitachi Province.
水戸家の支系（御連枝）は、讃岐国高松藩の高松松平家、陸奥国守山藩の守山松平家、常陸国常陸府中藩の府中松平家、常陸国宍戸藩の宍戸松平家の4家を数える。