As a young boy, his aunt Sophie, Electress of Hanover, found him neglected and miserable. His spirit had been crushed by his teachers, Spanheim and Pufendorf, and by his father, whom he could only please by behaving badly to his mother. At the age of seventeen he still had his knuckles rapped by his governor's ruler. 
It was his aunt Sophie who suggested Princess Vilhelmine Ernestine of Denmark as a possible bride. In Sophie's summing up she was simply brought up, modest to the point of never opening her mouth, god-fearing and extremely proper. The girl's enormous hips and bosom fell short of feminine perfection but at least suggested a capacity for producing babies. 
When the marriage took place, the celebrations took almost a week. Speeches, in Latin and German, requested of his uncle Ernst August, Elector of Hanover, to instruct him 'in matters which he did not understand'. However, Karl was an inept pupil and Vilhelmine Ernestine never became pregnant. Later on there was some doubt whether the marriage had been properly consummated. 

When his father's second wife, Louise, was dying, he swore he would look after his half-sisters. However, this promise meant very little as Karl was becoming very odd. His wife, Vilhelmine Ernestine, made it a point of honour to show the dying Louise that she regarded her as a sinner. While Vilhelmine Ernestine was excessively devout, Karl developed a religious mania. He spent unreasonable hours at his devotions, but also sank to his knees for prayer in the middle of other activities. If his father wanted to discuss family or political matters, he would excuse himself, saying he did not understand anything about such things. He was a sad comparison, so different from his spirited, attractive but ineligible half-brothers. 
Later on the hypochondriac Karl developed a phobia for Vilhelmine Ernestine and was convinced that physical contact would give him nameless diseases. Karl was on a visit to England and, while receiving an honorary doctorate at Oxford, was told of his father's death. When he was back in Heidelberg he did not fulfil his promise to Louise and did nothing positive for his half-sisters. He was Elector Palatine for only five years and died childless, aged only thirty-four.
 

Source: Leo van de Pas