Hesse-Rheinfels was created as a cadet line of Hesse for Philip II, Landgrave of Hesse-Rheinfels (1541–1583), landgrave from 1567 until 1583, and as a cadet line of Hesse-Kassel for Ernest, Landgrave of Hesse-Rheinfels (1623–1693), landgrave from 1627 until 1658.
Philip was the third son of Philip the Magnanimous, Landgrave of Hesse and Christine of Saxony (1505–1549). After his father's death in 1567, the Landgraviate of Hesse was divided between the four sons out of the late landgrave's first marriage. Philip the younger received the portion around the Rheinfels Castle and city of St. Goar on the left bank of the Rhine. From there he controlled the towns of Schotten, Stornfels, Bad Homburg, Lißberg, Ulrichstein, Itter, and the part of the former high noble and remarkably rich County of Katzenelnbogen north of the river Main.
Maurice the Learned (1572–1632) was Landgrave of Hesse-Kassel from 1592 until 1627. Maurice turned to Calvinism in 1605, became involved later in the Thirty Years' War, and, after being forced to cede some of his territories to the Darmstadt line, abdicated in 1627 favour of his son William V (1602-1637), his younger sons receiving apanages which created several cadet lines of the house (Hesse-Rotenburg, Hesse-Eschwege and Hesse-Rheinfels), of which, with amalgamation, that of Hesse-Rheinfels-Rotenburg survived till 1834.
In 1627 Ernest (1623–1693), a younger son of Maurice, Landgrave of Hesse-Kassel, received Rheinfels and lower Katzenelnbogen as his inheritance, and some years later, on the deaths of two of his brothers, Friedrich, Landgrave of Hesse-Eschwege (1617–1655) and Herman, Landgrave of Hesse-Rotenburg (1607–1658), he added Eschwege, Rotenburg, Wanfried and other districts to his possessions.
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