Wow… I've got to say that I'm quite happy with this outcome… it was originally supposed to be a character sketch… and then it turned into this. It's a bit of a different point of view on the Dursleys than your usually used to, and I was a bit mean to Vernon…
The Lesser of Two Evils
Petunia Dursley knew she was a terrible mother, and Petunia Dursley knew that she was a terrible aunt. And deep down, Petunia Dursley knew she was a terrible person for not doing more.
If there was one thing Petunia Dursley was good at, it wasn't being a mother. It wasn't being an aunt either, but she felt she was better at one than the other.
Dudley. Her son was spoiled. He had everything he wanted, and everything his father wanted him to have. Her son was a mirror image of his father, both in appearance and behaviour. Not that she didn't love her husband, but she never pinned him as the best role model for her son. Both her husband and son were bullies, and she had wished with all her heart her son wouldn't inherit that trait from Vernon. She loved her son, but she admitted— if only to herself— that Dudley was a brat of the worst sort.
Harry, on the other hand, was severely mistreated, probably considered neglected, and was on the borderline of abused. He wasn't allowed to do better than Dudley in school. He worked long hours in the garden, and then equally long hours inside. He was expected to help with dinner every night, and he was expected to eat as little as possible. Dudley was encouraged by both parents to beat on the smaller boy, which he did at every chance he had. At night, Harry was to curl up in the cupboard under the creaky stairs on his small cot, and then Petunia would lock him in with the spiders until morning. The locks on his door were old and rusty, and when they opened, the entire house could hear them. To him, it must have felt like he wasn't worth new locks.
That wasn't all though. Harry was lied to on a daily basis. They told him his parents died in a car crash. They told him they were drunks who were a menace to society. But the one thing they didn't tell him was his parents' names. Petunia doubted that James had been in a car once in his life, and she knew for a fact that Lily didn't' drink. Lily was much too afraid of alcohol. Her friend, Severus Snape, had a father who drank. Petunia could remember the horror stories of what happened behind closed doors that she'd listen in on.
It could have been worse for Severus Snape, Petunia knew. At least Severus Snape had the freedom to go where he wanted to go, to know what he wanted to know. Severus Snape was allowed to tell his friend about his home life because his father didn't care that he did. Heck, Severus Snape was allowed to make friends. She knew for a fact that she and Vernon didn't give that to Harry. She and Vernon didn't give any of that to Harry.
But there were things that she did just for Harry.
If she allowed Harry to do better than Dudley at school, Dudley would be jealous and would use it as an excuse to beat on Harry even more than he already did.
If she didn't make Harry work long hours in the garden, Vernon wouldn't let him out of the house outside of school. He didn't want the neighbours to see Harry.
If he didn't do the housework inside, Vernon would have him locked in his cupboard instead.
If Harry didn't help cook dinner every night, Vernon wouldn't be as willing to let Harry eat as much as he did let Harry eat.
If Petunia hadn't encouraged Dudley to beat on Harry, then Vernon would do it himself.
If she didn't lock Harry inside the cupboard every night with the rusty old locks, she didn't know what would happen. The creaky stairs were another precaution; her husband's weight made it painfully obvious that he was walking down them. She wished she could've just locked him in a bedroom, but there wasn't one on the first floor. She loved her husband with all her heart, but she wasn't going to lie about what kind of person she knew he was.
She didn't want to tell Harry what he was because ignorance is bliss. If Harry knew he was a wizard he would ask questions about it. If Harry asked questions about wizards and witches and magic, Vernon would get mad. A mad Vernon made not a peaceful household.
She told him his parents were drunks that died in a car crash because Harry was too young. Harry was too young to know that his parents were killed by an insane psychopath bent on ruling the world because he was a wizard. Harry was too young to be worrying about those kinds of things. She knew Harry would learn the truth someday, so why must she tell him something so worrisome so young?
And the reason that she didn't tell him his parents' names? If asked, she would just smile, and out of the corner of her eye she would look at the fresh flowers on the mantelpiece that would come right out of her garden. In a beautiful, expensive glass vase two lily flowers would remain until they wilted and had to be replaced with two more fresh cuts. In the winter though, in their place sat an old, cheap, plastic petunia. She never told her husband where it came from or why she'd put it out every year.
Petunia believed herself to be a better aunt to Harry than she was a mother to Dudley. She knew she was a terrible aunt though, and an even worse mother. She knew that she could have done more for Harry if she really tried, and she knew that she didn't deserve to have the title of Aunt Petunia.
And secretly, Petunia Dursley hoped with all her heart that one day Harry would forgive her.