The Thief Lord (2006) on Netflix

Plot summary

When Prosper and Bo lose their parents, their aunt Esther takes them in and plans to keep only six-year-old Bo, sending Prosper, who is twelve, to boarding school. Prosper instead carries his brother off to Venice, the city their mother told them stories about. In the alleyways and canals the boys meet the Thief Lord, a masked teenager named Scipio, who brings them to the Stella, an abandoned cinema where three orphaned children live. The gang steals to support itself. The brothers' aunt and uncle, Esther and Max Hartlieb, come to Venice and hire the detective Victor Getz to find the boys. Scipio's newest client, a man called the Conte, wants a wooden wing stolen from a mansion.