when you were young and didn't tell...i found i felt i had to protect this info from others. i was too embarassed or ppl wouldn't believe me. i'm glad you were courageous and finally told your brothers. unfortunately if a family has a "pink elephant" in the room-abuse for example-the family members don't want to acknowledge it cause they too don't want to admit the disfunction of the family.
i'm sorry this continues to plague you and cause you to question "why". abuse in any form is not acceptable. my advice-how do you stay healthy in an unhealthy environment? answer-distance, is what my T told me. get on with your life and i encourage you to see a T that can help you resolve your questions and feelings. it helped me so much to do that. you are the heathy one, not your family, brothers included.