I'm a medievalist scholar, and I've studied the reigns of the early Plantagenet kings (Henry II through Edward III) quite in depth. Although they lived so long ago and inhabited a society radically different from our own, its amazing how their personalities came down to us across the centuries. In this thread, I'm going to discuss the Plantagenet kings and perhaps we will determine what some of their MBTI types were.
I'll start with King John, as I've studied him the most.
John was the youngest son of Henry II and Eleanor of Aquitaine, and is quite famous as a cultural icon from the Robin Hood fables, in which he appears as 'Evil Prince John'. The real John was, I'll admit, a greedy, paranoid little snot. What we know of his personality we learn from contemporary and near-contemporary chroniclers, most of whom had nothing good to say of him. He was his father's favorite before he betrayed him and broke his heart, and he seems to have had some personal charm.
Like his father and brother Richard, John inherited the famous Angevin temper. Richard of Devizes relates that John, then a prince, got so enraged at Chancellor Longchamp on one occasion that "his whole being so changed as to be unrecognizable. Rage contorted his brow, his burning eyes glittered, bluish spots discolored the pink of his cheeks, and I know not what would have become of the chancellor if in that moment of frenzy he had fallen into his hands like an apple as they sawed the air."
He had a cruel streak a mile wide. John hanged 27 Welsh hostages in 1212 after their fathers broke their word, had Jews tortured when they refused to give him a loan, and had William de Braose and his mother bricked inside their castle and starved to death. Even by the standard of his time John was ferocious when enraged, and he very likely murdered his nephew Arthur in 1203 during one of his rages.
He also had a rather bawdy sense of humor, such as when he held the clergy's concubines for ransom.
His attitude toward religion was shocking for a medieval monarch; most kings tried at least to give the impression of piety, but John couldn't even be assed to do that. The pope excommunicated John for defying him, and there was even a crazy rumor related in all seriousness by Matthew Paris, that John was planning to convert to Islam and sell England to the emir of Morocco. Such a thing was unlikely in the extreme, but gives you some idea of his devotion to Christianity, that people would think that of him.
John was paranoid and distrustful, and caused havoc by constantly changing his passwords that he would give his guards, only to forget them later. He was suspicious of his barons and trusted none of them. John was hyper-sensitive to the slightest offense and would go after people ferociously. He was also apt to take bribes (one of his barons, Robert de Vaux, bribed him with five horses in 1210 'to keep quiet about the wife of Henry Pinel').
John had a notorious reputation as a lecher, even by the standards of his day, when a king was expected to take mistresses. He had at least twelve known illegitimate children (a record surpassed in English history only by his own great-grandfather Henry I [who fathered almost thirty] and equalled by Charles II). It's worth noting that John seems to have taken good care of his many and sundry bastards; several of his sons became knights and married wealthy heiresses, one son became a priest, one daughter an abbess, and the other two daughters married a Cornish lord and a Welsh prince. He was so uncharacteristically generous to his baron William de Forz, who's mother was a known mistress of John's, that I half-suspect William de Forz was his biological son.
The relationships I'd like to linger on, however, were with his two Isabels: Isabel of Gloucester, his first wife, whom he divorced in order to marry Isabelle d'Angouleme, the heiress to the strategically important county of Angouleme. What's bizarre about this arrangement is that contrary to what you might expect, John didn't throw Isabel of Gloucester out of his castle, barefoot and weeping. Instead, she continued living at Winchester castle with him for several years AFTER they divorced, only leaving in 1207 when Isabelle d'Angouleme became pregnant. He supported his ex-wife with a household of staff and knights, lavished her with gifts, and gave her an annual allowance of £80 (quite impressive considering a contemporary English baron's annual income was about £200).
His queen Isabelle was treated quite poorly, however. He allowed her no French attendants and she had no control over her dower lands, nor any income from them. John firmly kept her from having any power.
John had a love of jewels that bordered on obsession. He kept his collection carefully inventoried and bought jewels whenever he could. John also liked reading, and hauled a library of books with him wherever he went. He bathed frequently and liked to be well-dressed; his contemporaries thought him something of a fop.
Despite his reputation as the worst of England's kings, John was very attentive to statecraft, in marked contrast to his brother Richard. He tried to solve the many political and financial woes afflicting the realm he had inherited, and retained most of Richard's more able staff as his own. He built and maintained England's navy. His talents were wasted by his own personality faults and the awful state England was in when he became king.
I'm thinking he was an unhealthy ISFP.