My bro had bad habits, now he is suufering from red patches inside his mouth which are not going , does it means cancer?

Red patches in: A young man is best diagnosed by a dentist, and more likley an infection than a cancer. Usually chronic inflammation can be a risk for oral cancers, and infections with hpv of throat cancers. But knowing, preventing, changing behavior is another thing.

Oral lesions: He needs to be seen by an ear, nose and throat doctor. He probably needs biopsies to see whether or not it is cancer.

See a physician: Bad habits? Depends what that is? Alcohol and tobacco (especially chewing) increases the risk of head and neck cancer. What is the age -- low risk in young, much higher in an older multi year user. See a physician -- primary care, ent, or oral specialist such as a dentist or oral surgeon.