Hello
You can see this thread:
eea-route-applications/eu-settlement-sc ... s#p1794742
It shows a successful application. However, for 1 successful application, you will find many other that have been refused.
The EU Settlement Scheme is not a magic tool where you can upload an Excel file with your family members and get a pre-settlement card for each. The Home Office pushes back very strongly such applications.
In case of failure of that immigration attempt, your parents and brother won't be able to get a visitor visa in the future. You have to weight this in the decision to go forward.