You are such a wonderfully strong person! The more you describe your situation as a child, I can see why your siblings don't suffer from the trauma. You shielded them and saved them. It was incredibly selfless of you and like you say, it shouldn't have been your responsibility to take on such a role but you did. That even answers your question of why did it happen! The child in you never really got the attention and love you've always given others. Stay strong! You're amazing!