A Slytherin in Lion's clothing
Had it been Petunia who had found the baby and the note on the doorstep, things might have been different.
However, Petunia had a cold in the nose, and Vernon went to fetch the milk in. He read the letter and felt an unwonted rage build up in him towards the small child on the doorstep.
Baby Harry did not like the big red face lowering and accidental magic rolled off him, blowing Vernon back to fall and sit heavily on his large behind, blowing away blocks on Harry's magic, Vernon's minor magic, and Dudley's magic – like does seek like, after all – and the compulsions embedded in the letter to treat Harry badly.
The memory charms vanished as well, and Vernon remembered the older brother he had forgotten who had received a Hogwarts letter and whom he had adored, and how horrified his parents had been about 'Satanism' and how Vince had become trapped in their caravan on holiday when it somehow went on fire, and his parents murmured that at least he had been cleansed by fire. And Vernon remembered that this was why he had rejected his parents' religion when he was adult. His problems with over-eating started then, as well. No arson had been detected, but Vernon wondered if his parents had performed the magic they despised under belief of it being prayer. Men in red cloaks had come and taken away those memories. He remembered them now.
"Well!" said Vernon, making his face display the jovial expression it was supposed to hold, "Let's see what we can do about this, shall we, young Harry? You've given me a gift, today, and maybe saved me from killing our Dudley with kindness. You and I are going to plot together, when you are old enough."
The years passed. Vernon networked with all those wizards who greeted Harry in the street. He learned to celebrate Samhain as a remembrance and had his new friends over to remember Lily and James – Vernon cared much less about James – and his brother, Vincent.
Vernon went through a trunk Petunia had kept with her diary, and discovered who had been friends with Harry's parents. Mr. Remus Lupin came as a lodger, after much persuasion, with a secure cell in the cellar, and taught at St Grogery's County Primary School as well as bringing on the Dursleys and Harry with as much magic as they could manage. He was known to have terrible migraines, related to the full moon, which was something to do with tidal drag. Vernon paid for him to have wolfsbane, and Remus helped Vernon to get the proper stipend for the carer for an orphaned heir.
For everyone but Harry, learning magic was mostly potions, and a few household charms; but Remus helped get Petunia registered as a hedge witch, since her ability was greater than her husband and son, and so the house was not subject to underage trace.
"It's not fair," Remus said. "Those of pure blood with very little more magic than a garden snail get into Hogwarts of right. But for first generation magic wielders life is harder." He considered. "I suspect that if it was anyone else, Dudley might have got a letter, but from what I've learned since associating with you, Dumbledore would be likely to suppress that, and work on his jealousy of Harry. I'm glad you let me see the original letter or I might have been loyal still to Dumbledore."
"I'm not sure I'd enjoy Hogwarts, anyway, Uncle Remus," said Dudley. "Other than being backup for Harry."
"If you really wanted to go, I'd discuss with you all about blood-adopting you so that nobody knew who you were," said Remus.
"He'd still be our son?" asked Vernon. "And not a werewolf?"
"Yes; he'd have two fathers," said Remus. "I did a heap of research and the lycanthropy does not pass in blood but solely in the saliva. And only in wolf form. If, for any reason, I bit someone in my human form, the disease would not pass. I can't imagine who has done experiments about that," he said, grimacing.
"Then it's up to Dudley," said Vernon.
"I'd as soon not go," said Dudley.
"Logged as 'home schooled," said Remus.