Hi, I'd like to help you with your question.
If you are feeling suicidal and feel you cannot wait until you see your counselor, it is a good idea to present yourself to the emergency room for an evaluation. At the very least you may be able to be prescribed medication (or a change in medication) to help you until your therapy can be effective.
You are correct, it is very common for those without mental health issues to see those with them as hard to explain or hard to cope with. Since others in your family have no way of understanding mental health, then they try to explain your symptoms away in the least distressing manner. That is probably what you ran into when you tried to explain your situation to your family.
Regarding your possible Bipolar disorder diagnosis, have you ever experienced a hypomania episode? This is necessary before you can be considered Bipolar (as you probably already know). It sounds like you need a new evaluation to determine what exactly is your diagnosis so you have a better chance of addressing it with medication, therapy and self help.
Bereavement can complicate matters when you already have depression. The fact that your mother committed suicide violently and that your brother is also experiencing similar symptoms, plus the loss of his partner, puts enormous stress on you. If you are in a caregiving role in your family, this exasperates the situation even more.
It is good that you are starting therapy soon. But as you begin the process, you can also help yourself feel better by taking some steps to build up support and guidance. Here are some resources to help:
Some books that may help:
The Mindful Way through Depression: Freeing Yourself from Chronic Unhappiness by Mark Williams, John Teasdale, Zindel Segal and Jon Kabat-Zinn
Undoing Depression: What Therapy Doesn't Teach You and Medication Can't Give You by Richard O'Connor
The Cognitive Behavioral Workbook for Depression: A Step-by-step Program (Workbook) by William J. Knaus and Albert Ellis
You can find these books on Amazon.com or your local library may have them for you.
Finding support through support groups and relying on others who understand loss and depression will help you work through your symptoms. And, if you wish, you can share these resources with your brother as well. Relying on each other may help you both recover and feel more positive about the future.
I hope this has helped you,