From the middle ages, there were several princely houses, including the Yotsutsujinomiya and the Iwakuranomiya, which were not the Seshu-Shinno-ke, but Seshu-Miya-ke (hereditary princely houses) because they did not always succeed to the title of Imperial Prince.
中世以来、四辻宮や岩倉宮などいくつもの宮家が存在したが、これらの宮家は親王の身位とともに継承されるとは限らないので世襲宮家ではあるものの、世襲親王家ではない。