After Yoshitaka OUCHI in Suo Province killed himself because of the rebellion of his vassal, Takafusa SUE (Harukata SUE), in 1551, Yoshishige accepted the proposal of Takafusa to have his brother, Haruhide OTOMO (Yoshinaga OUCHI) become the new family head of the Ouchi family.
天文20年（1551年）に周防の大内義隆が家臣の陶隆房（陶晴賢）の謀反により自害すると、義鎮は隆房の申し出を受けて弟の大友晴英（大内義長）を大内家の新当主として送り込んだ。