The origin of vedanta schools

MADHVACHARYA Founder of dvaita
SRI RAMANUJACHARYA Founder of visishtadvaita

I think, the difficult question regarding Vedanta is about its origin. Some scholars sticks to a  view on its beginning from Vedas. More strictly, from Upanishads. But which Upanishads? It is still difficult to assert or refute. None among the ten principal Upanishads strictly follows the doctrines of any Vedanta schools in strict sense. It was in the Brahmasutras of Badarayana Vedanta became an organised system. Later different teachers interpreted it according to their different views, which resulted in the formation of different branches, namely Advaita Vedanta, Visishtadvaita Vedanta, Dvaitavedanta etc.