June 23rd marked Dudley Dursley's 35th birthday, and in celebration of that fans got more information on Pottermore about the Dursley's and why they are the way they are, not to mention the origin of their names.
When speaking of why she named the characters what she did she says that
Vernon was a name I never cared for while Petunia is a name I always gave unpleasant characters in games of make believe she played with her sister. "Dursley" was taken from the eponymous town in Gloucester and is more about the sound of the word rather than any association with the place.
When Petunia and Vernon were engaged, she was nervous about what he would think of her sister, who was dating James at the time. Being what his character is, I am sure that it is no surprise to fans that he tried to belittle James and asked him what kind of care that her drived. James described his broom and when he described the wizard's bank, Gringotts, Vernon assumed that he was making fun of him.
His dislike of Harry actually comes from the same place as Professor Snape's, that he looks too much like his father.
The issues didn't end there, as sibling rivalry never ends even after the children are grown. Just like when they were growing up, Petunia felt that Lily was always outshining her, and so didn't choose her own sister to be her bridesmaid when she got married. The only time they spoke after that was when the Dursleys received Harry's birth announcement.
Rowling actually said want to show a nicer side to Petunia when she said goodbye to Harry in The Deathly Hallows, but thought that that would go to far away from the character that she had already established. I, for one, would have liked to see her apologize for the way that she had treated Harry and maybe say that she regrets it.
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