I am sorry for your situation. The good thing is that you may apply to remain in the UK on the basis of a 'retained right of residence', even if your brother got divorced. One of the following must apply:
1. the marriage lasted at least 3 years before legal proceedings began and the couple lived in the UK for at least 1 year before the divorce was finalised;
2. he has custody of a child;
3. he has access rights to a child, provided the child is under 18 and a judge has ordered that access must take place in the UK;
4. you, or a family member, have been a victim of domestic violence during the marriage or civil partnership, or there are other particularly difficult circumstances which justify retaining the right of residence.
If any of these apply to you, the application process is explained here: https://www.gov.uk/family-permit/apply . On point 7. (retained rights of residence) you will find the confirmation of what I have said above. Note that you will need, in particular, the divorce document of your brother.
I hope my answer was useful and look forward to your rating, which is essential to my activity.
Dr I L Vlad