Possible Protestant Candidates:
- Elizabeth Charlotte of the Palatinate (1597–1660) is the sister of Frederick V, Elector Palatine who married Elizabeth of England, Charles' older sister.
- Sophia Eleonore of Saxony (1609-1671) daughter of John George I, Elector of Saxony, and Magdalene Sibylle of Prussia
- Elizabeth (1610–1674) is the oldest daughter of Esmé Stewart, 3rd Duke of Lennox and his wife Katherine Clifton, 2nd Baroness Clifton
- Princess Maria "Elizabeth" of Sweden, daughter of King Charles IX of Sweden.
- Catherine of Brandenburg (1604-1649) daughter of John Sigismund, Elector of Brandenburg and Anne of Prussia.
- Lady Anne Hamilton (c.1603) daughter of James Hamilton, 2nd Marquess of Hamilton and Lady Ann Cunningham, herself a daughter of James Cunningham, 7th Earl of Glencairn
- Dorothea Augusta of Schleswig-Holstein-Gottorp (1602-1682) a daughter of John Adolf, Duke of Holstein-Gottorp and Princess Augusta of Denmark, making her a cousin via King Frederick II
- Anne Eleonore of Hesse-Darmstadt (1601–1659) or Sofie Agnes of Hesse-Darmstadt; (1604–1664) daughters of Louis V, Landgrave of Hesse-Darmstadt and Magdalena von Brandenburg
- Dorothea of Anhalt-Zerbst (1607-1634) daughter of Prince Rudolf of Anhalt-Zerbst (1576–1621) from his first marriage to Dorothea Hedwig (1587–1609), daughter of the Duke Henry Julius of Brunswick-Wolfenbüttel.
- Dorothea of Brunswick-Wolfenbüttel (8 July 1596 – 1 September 1643) daughter of Henry Julius, Duke of Brunswick-Lüneburg and Elizabeth of Denmark, another daughter of King Frederick II
- Charlotte (1599–1664), daughter of Claude, duc de Thouars and Countess Charlotte Brabantina of Nassau, herself a daughter of William the Silent and Charlotte of Bourbon
- Amalie Elisabeth of Hanau-Münzenberg (1602–1651) daughter of Philip Louis II, Count of Hanau-Münzenberg and Countess Catharina Belgica of Nassau.