The founder of the Simmern line, Stephen, Count Palatine of Simmern-Zweibrücken is also the founder of the cadet branch House of Palatinate-Zweibrücken and its cadet branches.

The house of Palatine-Simmern, in the person of the 1st elector, Frederick III, were staunch Calvinists.

Frederick III was a devout convert to Calvinism, and made the Reformed confession the official religion of his domain by overseeing the composition and promulgation of the Heidelberg Catechism.

His support of Calvinism gave the German Reformed movement a foothold and base within the Holy Roman Empire.

As of 2022[update], those in the line of succession to the British throne are Protestant descendants of Sophia, who was born into the house (daughter of Frederick V and Elizabeth Stuart) as Princess palatine of the Rhine, later becoming Electress consort of Hanover[1][2].