I take it your brother has passed away. If he is married or has children, you probably have no legal rights as his sibling. But if he was unmarried and childless, and your parents are not alive, then you and your other siblings, if any, are his next of kin. In that case, you are entitled to notice of any probate proceeding. However, that does not necessary give you rights regarding his trust, retirement plan, or life insurance policies because they may well have named beneficiaries and not go through probate.
Harry S. Margolis practices elder law, estate, and special needs planning in Boston and Wellesley, Massachusetts. He is the founder of ElderLawAnswers.com and answers consumer questions about estate planning issues here and at AskHarry.info.