How do I deal with the loss of my Mother and Brother who passed within a two year period? I need medical help I can't bear with the loss.

The death of both your Mother and Brother is a very great loss.  No wonder that you and your Sister are both grieving.  It might be that your Sister is coping with the deaths by NOT talking about them which is different from the way that you are grieving.

One grief support group that I attended after my Mom died was GriefShare.  (Copy and paste URL to your browser.) 

https://www.griefshare.org/about

GriefShare is for people grieving the death of a family member or friend.  It is a small group of people who meet weekly for several months.  You watch a video and then discuss your feelings about the video.  There is a Workbook with assignments for each video along with practical ways to cope with Holidays, etc. 

They also offer free daily Emails with inspirational messages and practical information as you grieve the loss of your loved one.

Berean Chapel of Detroit, 8422 Pembroke Ave, Detroit, MI is scheduled to have a GriefShare group on Jul 25, 2019 – Nov 7, 2019 on Thursdays at 6:30 pm.
You might want to contact them about their next meeting.  Although the meetings are held in a church and the videos have religious content, the group is not there to "convert" you to their denomination. 
{{{HUGS}}}

I am so sorry for your losses, that is a lot to carry in a short period of time. Please know that each person grieves in their own way, your sister may be dealing with her own grief and we cannot save someone from drowning if we are drowning ourselves.

The best option may be to join a grief support group, most hospitals can direct you to a list of them in your area - some even have groups that meet at the hospital. One thing that helped me was to keep a journal and just write down all the crazy whorl wind emotions, thoughts, and dreams that tried to take me down. It can take up to four years to grieve through a loss so if you can, engage in something you enjoy, take some classes, and get some exercise. You have to care for YOU now.

babycake - I am so sorry for your loss. Your brother was too young when he passed away. Since you have spent many years as a caregiver, it is a big change to not have someone to care for. But it is time you care for yourself. Please go see your doctor right away and tell him/her about your depression. He/she will know of resources that can help you.

Thank you

I Googled "Mental Health Care Detroit" and found the Detroit Wayne Mental Health Authority.  Copy and Paste the URL to your browser for information about services available.

https://www.dwmha.com/

The Detroit Wayne Mental Health Authority is a safety net organization that provides a full array of services and supports to adults with mental illness, individuals with intellectual and developmental disabilities, children with serious emotional disturbances and persons with substance use disorders. DWMHA provides empowerment to persons within our behavioral health system, serving nearly 75,000 citizens in Detroit and Wayne County.