Kobu gattai
Japanese: 公武合体 (Koubu Gattai)
Kôbu Gattai refers to marital ties between the imperial family and the shogunate . It was a political theory during the Bakumatsu period.
In 1861, Shôgun Iemochi married Princess Kazunomiya who was a sister of Emperor Kômei.
The Kôbu Gattai marriage didn't last very long because both Iemochi and the Emperor died within 5 years.