PARIS — On a recent evening, Amar Sitayeb squeezed behind a tiny counter at the minimart that he and his older brother Ali have run for more than 35 years in the Marais district of central Paris. A plump gray tabby cat prowled the floor, and faded photos of neighborhood babies, many now grown-ups, were taped to an old cash register.

A stream of regulars filed in, grabbing potato chips, gum and soda, and lingering to exchange gossip and pleasantries. One neighbor with the sniffles bought honey and tea. Mr. Sitayeb fished mint for her from a refrigerator. “This should help,” he said.

Ten minutes later, she returned and asked for rum. “That’ll attack the cold quicker!” he laughed, pulling a bottle from the shelf.

The purchases were mainly an excuse to spend precious moments bantering with the Sitayeb brothers, known to residents around the rue Sainte-Croix de la Bretonnerie, a boutique-studded Marais street, as the eyes, ears and unofficial mayors of the area.