Yusai, Tadaoki's father was defending Tango-Tanabe Castle in Tadaoki's absence and came under siege (the Battle of Tanabe Castle), however, in accordance with an imperial order from the Imperial Court, he gave up the castle prior to the Battle of Sekigahara and was taken to Tanba-Kameyam Castle which was controlled by enemy commander Shigekatsu MAEDA.
また、父の幽斎は忠興の留守を守り丹後田辺城に籠城したが（田辺城の戦い）、朝廷からの勅命により関ヶ原の戦い前に開城し敵将前田茂勝の丹波亀山城に入った。