Alex was nine when he started the coffee can.
He found it in the trash bin one morning after Maria had finished the last scoop for her thermos. The label was peeling, but the lid snapped tight. He washed it out quietly at the sink, dried it with a dishrag, and took a marker to the side: SOFIA, in big block letters.
He slid it under his bed, next to his shoebox of baseball cards.
Sofia was seven, still small, with a cough that came and went like bad weather. The inhaler helped when they could get it refilled. Maria worked extra shifts for those months, but sometimes the money ran short anyway.
Alex saw how it wore on her the way she'd rub her temples at the table, staring at the bill like it might change if she looked hard enough.
So he started filling the can.
Bottles from the park after school, turned in for nickels at the recycling spot. A quarter from Mr. Ramirez for sweeping his stoop. Fifty cents for walking Mrs. Diaz's dog around the block.
Every coin went in.
Clink.
Sofia found out one night.
She'd woken up coughing, and Alex was the one who got the inhaler from the bathroom, held it for her until her breathing eased.
"What's that under your bed?" she asked after, peering in the dark.
He pulled it out, showed her the label.
"For you," he said. "Medicine money. In case."
Her eyes went wide. Then she hugged him, skinny arms tight.
"You're my hero, Alex."
He ruffled her hair, pretending it didn't make his chest ache.
After that, they'd add to it together sometimes Sofia finding a dime on the sidewalk, Alex splitting his bottle money.
They didn't tell Maria. It was their thing.
The can got heavier.
And so did the promise.