Mary Stuart, Princess Royal, with her husband William of Orange. Their marriage took place on 2 May 1641 at the Chapel Royal, Whitehall Palace. London. Mary was the first English princess to be granted the title, Princess Royal, in 1642.
John William Friso, Prince of Orange (1687 - 1711). Prince of Orange from 1702 until his death in 1711. After the death of William III there were no male heirs of William I left, so the throne when to John William Friso, a descendant of William I's brother. He married Marie Louise of Hesse-Kassel and had two children.
1574-55 Mary Stuart by Federico Zuccari (or Zuccaro). Need to research this further. Ah! Having done so, this is a portrait awaiting a better attribution. It's not Mary Queen of Scots and it's not Elizabeth.