Are brain tumors hereditary, if not, what causes them?

Generally not: Brain tumor are usually not hereditary. However, there are certain syndromes where there is a well known genetic link. In such situations, because the patient's inherit the genetic problem, they also inherit the increased risk for brain tumors.For example, li-fraumeni syndrome, or neurofibromatosis i are examples of syndromes where there is an increased risk of brain tumors amongst family members.

Very few: The cause of most brain tumors is unknown, but it is fairly clear that most are "sporadic", not caused by an inherited abnormalities. A small number of cases are, however, clearly caused by inherited genetic defects. Many of these present in childhood, not in adult life, but certain genetic syndromes cause adult tumors of specific types. You can get more details than this space allows.