Queen Elizabeth II is dead, God rest her; and her son Charles Philip Arthur George reigns as King Charles III.
Why does that name bother me? He could have decided to use any of his names; his grandfather, George VI, was called Albert Frederick Arthur George, and chose to reign as George. So if Charles Philip Arthur George chooses to reign as Charles III, why not? Who was Charles II? For that matter, who was Charles I?
I warn you, succession to the British throne depended on primogeniture (who is the eldest legitimate child - a son, for preference; daughters only succeed if there are no sons). So this gets really complicated. I've gotten all these details from Wikipedia.
When Queen Elizabeth I died without issue in 1603, the Tudor royal family was extinguished, and the next family with an actual claim to the throne was the Stuarts, represented by James VI of Scotland (1567-1625). He added the title James I of England and Ireland when he succeeded (1603-1625).
James was the son of Mary, Queen of Scots and her King Consort, Henry Stuart, Lord Darnley, who had a claim to the English throne through a grandmother, Queen Margaret Tudor, daughter of King Henry VII of England. And when James VI and I died in 1625, his oldest surviving son Charles succeeded him as Charles I.
Charles I (1625-1649) was born in Scotland but moved to England after his father inherited the throne. His reign was tumultuous and relatively short - he believed firmly in the divine right of kings, and he argued with the English Parliament almost immediately. For one thing, he believed he could impose taxes without consulting Parliament. He also married a Catholic (Parliament was heavily Puritan), although he supported High Anglican clerics. He went to war with Parliament's New Model Army (look up Oliver Cromwell), lost a couple of times, and was tried, convicted, and executed for treason in January 1649.
We've all just learned that the crown passes to the heir immediately on the king or queen's death. But not in this case; the country was at war. Charles II was proclaimed King of Scotland by the Scottish Parliament on 5 February 1649. There was no King of England and Ireland during the period called the Interregnum or English Commonwealth, which was a de facto republic led by Oliver Cromwell.
Charles II lost the Battle of Worcester to Cromwell on 3 September 1651 and ran to the Continent, spending the next 9 years in exile in the coastal countries facing Britain. Cromwell died in 1658, producing a political crisis that led to the restoration of the monarchy and an invitation to Charles II to return and rule, which he did. He was 30. He ruled until he died in 1685, quarrelling regularly with Parliament about religion, especially after his brother James became a Catholic. He left no legitimate children (but at least 12 illegitimate!).
That was the end of the Charleses, and pretty much of the Stuart dynasty. James II succeeded his brother Charles in February 1685 and was deposed in the Glorious Revolution of 1688, mainly because he was Catholic and had just had a son, which meant he could found a Catholic dynasty. In 1688 Parliament invited William of Orange (a Protestant grandson of England's Charles I, married to James II's eldest daughter) to invade, which led to James eventually settling in France and William and his wife Mary taking over the throne by invitation, after a not very serious battle. Neither one lived very long and they were succeeded by Anne, James' youngest daughter) for about 5 years.
But the Stuart dynasty produced one more Charles, who tried to become Charles III in the 1760s: Charles Edward Stuart, also known as Bonnie Prince Charlie. He didn't do very well at it but he made a lot of noise. Just read the Wikipedia article.
At this point I'll quit listing kings. In 1714, after Queen Anne's death, the House of Hanover was invited to the throne, because the Elector of Hanover was married to the granddaughter of James I and VI and heiress presumptive to the throne. Believe it or not, the Hanovers are still on the throne. Queen Victoria was in the Hanover line; the family name changed to Saxe-Coburg-Gotha when she married Prince Albert of that house. And yes, it's still there - Saxe-Coburg-Gotha became Windsor in 1917, by royal proclamation. In 1917 it was a little embarrassing for the royal house of Britain to have a German family name. So King Charles III is of the house of Windsor, once upon a time Hanover.
But every time I see "King Charles III", I think of Bonnie Prince Charlie. I wish the new King Charles III better luck than the Bonnie Prince had.