On 26 June 1578 Simon married Armgard, reigning countess of Rietberg and widow since 1575 of Erik V von Hoya. Simon was reigning count of Rietberg from then on. In 1579 he became emancipated and was recognized as Count of Lippe by the Landtag of Lippe. After the death of Armgard on 13 July 1584 Simon had to give up the County of Rietberg, as his marriage had remained childless. On 13 November 1585 he remarried with Elisabeth von Schaumburg. They got 10 children: 5 boys and 5 girls.