Dear Dr. Today My Brother Got Bitten By My Pet

Dear Dr. Today my brother got bitten by my pet dog second time within a period of 15 months. first time he got three injections of anti rabies again he got his hand bitten however the dog was given anti rabies vaccination in last November. How serious is this bite and under these circumstances is there any need for anti rabies vaccination again to him. This dog has bitten almost half of my family members and Labrador dog is very lovely and smart. He never goes out of house even doors are open. What makes him so aggressive and unpredictable and bites any member without giving any warning. How to control his such behaviour and tendency of biting.
Sham Sher Thakur.