Onarigami faith - Onarigamishinko

Japanese: オナリ神信仰 - おなりがみしんこう

...When we look at various family systems from the perspective of sibling relationships, we can broadly divide them into two types: those that emphasize or respect solidarity between siblings in some way, and those that promote separation between siblings and instead emphasize or respect parent-child and marital relationships. Family systems that emphasize sibling relationships that are particularly noteworthy are the extended family system, clan organizations, Onari God belief, equal inheritance, levirate marriage (brother-reverse marriage), and sororate marriage (sister-reverse marriage). The most common form of extended family system in Japan is one in which multiple male siblings remain in their natal home after marriage with their spouses (multiple children remaining), forming the same family, and it can be said to be a family in which solidarity between siblings is emphasized in addition to parent-child relationships. ...

From the Hime-Hiko system

...It was believed that sisters had the spiritual power to protect their brothers. This relationship can be clearly seen in the Okinawan Onarigami faith, which still exists today. Based on this relationship, a ruling system was created in which brothers and sisters shared political and religious power.

*Some of the terminology explanations that refer to "Onari God Belief" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…さまざまな家族制度を兄弟姉妹関係を視点としてみれば，兄弟姉妹間の連帯をなんらかの形で強調もしくは尊重するものと，兄弟姉妹間の分離を促進し，そのかわりに親子関係や夫婦関係を強調もしくは尊重するものの二つに大別できる。　兄弟姉妹関係を強調する家族制度としてとくに注目されるのは大家族制(拡大型家族)，同族組織，オナリ神信仰，均分相続制，レビレート婚(兄弟逆縁婚)，ソロレート婚(姉妹逆縁婚)である。日本における大家族制の最も一般的な形態は兄弟姉妹のうち複数の男の兄弟が結婚後配偶者をともなって生家にとどまり(多子残留)，同一の家族を形成するものであり，親子関係に加えて兄弟間の連帯が強調される家族といえる。…