Why do febrile fits happen and can it be avoided?

My elder brother had febrile fits every month until he was 29 years old and passed away. For his case, it was due to medical condition, epilepsy. For normal child, febrile fit will occur if fever is too high. If a child is prone to febrile fit, please be very alert everytime when he/she is having fever. Try all means to keep the fever lower e.g. feed medicines, cold bath and etc.