Aunt May has known from the start.
They don't talk about it, not ever, but eventually she stops bugging him when he disappears at night. She'll sit in his empty room, wrap herself in an old sweater of Ben's, and wait for him to come home.
He doesn't know that she knows, but she likes it that way.
It's hard for her to watch him come home, night after night, bloodied and bruised. She remembers when she first began to realize what was going on – he came home with a bullet in his leg and a carton of eggs and he gave her his silly award-winning smile.
She'd been watching the news. She knew Spider-Man had been shot.
And the next morning, when he came downstairs looking much better, cuts and bruises faded and gone, she knew.
She doesn't understand why he does what he does, but she understands that he thinks he has to. It's like what Ben said, before he died.
Peter has a gift, and he has a moral obligation to use it.
So she lets him, even though it hurts her. Even though it hurts him too.
One day he disappears, gone for a week. She watches the news religiously, knowing it will appear if Spider-Man has died. But it doesn't. He's just gone.
She even calls his girlfriend, that lovely girl Gwen. Gwen hasn't heard from him either, but she's worried sick. They commiserate over how silly it is that he insists on putting on that red and blue costume and saving the world. Somehow, it's easier to talk to Gwen than to tell Peter she knows.
His grades begin to slip, and normally she would tell him off, but now that she knows what he's doing... If he thinks it's more important to save lives than to study geometry, she understands. He's a bright boy. He knows what he's doing. She read somewhere that Spider-Man invented his own webbing. The thought makes her swell with pride. Her nephew, saving the world one web at a time.
Some of her friends in the knitting club hate Spider-Man. They bash him, calling him a horrible, ugly villain. And she takes every opportunity to defend him. Even without speaking to Peter about it, she knows he's doing good.
One night, Peter stumbles into his bedroom, more battered and bruised than ever, with a broken arm and a huge cut on his forehead. He throws off his dirtied, torn costume and crawls into bed.
In the morning, when he wakes, his costume is dry-cleaned and hanging on the doorknob.
He knows who it is immediately. At first he panics, but then-
It doesn't matter. She knows, and she's accepted it quietly.
Gunshots are loud, and giant mutant rhinos are loud, and running through the streets beating up criminals every night is loud.
But Aunt May stays quiet.