He was the second eldest son of Count Simon VII of Lippe and his first wife Anna Catherine of Nassau-Wiesbaden.
After he returned to Detmold in 1631, he applied to Emperor Ferdinand II to be declared of age early.
Influenced by his chancellor Christoph Deichmann, Simon Louis gradually moved away from his father's cautious policy of neutrality and approached Sweden.
Since Simon Philip was still a minor, Count Christian of Waldeck was appointed as regent again.
On 19 June 1631, Simon Louis married Countess Catherine of Waldeck (1612-1649), the daughter of his guardian Count Christian of Waldeck-Wildungen, and also a younger sister of his stepmother, Maria Magdalena (1606-1671).