I don't know how I ended up on this site and on your page, but maybe I can say a word of hope that will answer some of the questions and feelings you are experience about the death of your sibling. I have experienced being bi-polar a good part of my life and now I am in my 60's. When the high side of feelings are present, things are wonderful and happiness just reigns in emotions. On the other side is depression, and that can come on very quick, for what appears to be no reason, and thoughts of suicide come upon some people very fast. Because a person cannot understand why they are having those feelings, they will feel down, maybe plan a suicide, or maybe get through it, but each time the down feeling appears, so do the suicide feelings. When a person does act on the suicide, it is spontaneous, unexplainable, but an urge that the person cannot help but act upon. If they could reason their feelings, it would allow them to get help, but if they could use reasoning, they most likely would not have acted on those suicidal feelings. When you question as to why your sibling didn't come to you, it is most likely that the condition and compulsion was too strong to reason enough to talk to those who loved them. They weren't able to process in their minds the end result of pain it would cause everyone. Their thoughts of suicide, feelings, and urges were very real to them, but to a person who has not suffered from bi-polar would have difficulty understanding those feelings. Never blame yourself or wonder why. Your sibling probably couldn't answer that question either. I hope this helps to answer some questions and helps bring some peace to your life. Remember, the brain, just as any organ, is just another part of the body and can get sick. Just as we cannot always determine when a body part becomes sick, it is even harder to recognize when it is the brain that becomes sick. Turn to God and know that your sibling is with Him in a very safe place. Live your life knowing that you are not responsible for the actions of others and you do not have control over their thoughts either.
God Bless You and remember good times.