Big Hero 6

Hiro Hamada is a 14-year-old robotics genius who lives in the futuristic city of San Fransokyo and spends his time participating in back-alley robot fights. His older brother Tadashi, worried that Hiro is wasting his potential, takes him to the robotics lab at his university, where Hiro meets Tadashi's friends, GoGo, Wasabi, Honey Lemon, and Fred as well as Baymax, a personal healthcare robot Tadashi created. Amazed, Hiro decides to apply to the school. He presents his project—microbots, swarms of tiny robots that can link together in any arrangement imaginable—at an annual exhibition to gain admission. Professor Callaghan, head of the program, is impressed, and Hiro gets in. When a fire breaks out at the university, Tadashi rushes in to rescue Callaghan, but the building explodes and both are killed. As a result of losing his brother, Hiro secludes himself from others.

=====================================================================