What are my brother’s options if he is on B1/B2 visa and would like to convert to H1B next year?

Generally, a person otherwise eligible for an H1B (with a qualifying employer who wants to sponsor him) may apply to change status in the U.S. Details about eligibility and about the application process can be quite complex. It would be wise for the employer and your brother to consult with an immigration attorney who, after learning all of the relevant details about your brother, his job skills, the job, the employer, etc., would be able to advise about eligibility and would be able to offer legal representation.