It is commonly accepted that when the Soryo system (a system in which the eldest son would succeed as head of the family) collapsed, the branch families began to act independently from the main line of the house, which led to them maintaining relationships with other branch families by forming ichizoku ikki (family ikki) with them, and this is said to have developed into the forming of kokujin ikki based on territorial connections.
通説的には惣領制が崩壊し、庶子家が独自の動きを取り始めると一族一揆を結ぶことで庶子家との繋がりを維持したが、やがて地縁による国人一揆へと発展したと言われる。