ARTHUR I
1187 - 1203 (?)

Arthur the First didn't live too long as he was in the way of his uncle John.

Arthur was Duke of Brittany. This is the map location of Brittany:

BRITTANY, FRANCE

Arthur's grandfather was famous English King Henry II. His father was Geoffrey IV, his uncles were Richard Lionheart and John, who most likely arranged his premature death. Why would John do such a nasty thing?

Because Richard was king and didn't have any kids of his own. So Richard announced that Arthur would be heir to the English throne. John made a long face but not for too long.

Arthur was captured by John in battle at Mirebeau-en-Poitou on August 1, 1202, and subsequently imprisoned / murdered.