Retained right of residence for Brazilian living in UK as family member of an EEA national?

[ObliviousPenguin01]

I am a Brazilian citizen that came to the UK in December 2007 at the age of 14. My mother is also a Brazilian citizen and had been married to a Portuguese citizen, thus granting us both stay on the basis of being family members of an EEA national. However, although my mother married said Portuguese individual in 2007, they ultimately divorced in April 2015 with a decree absolute. Due to a mix up made by her lawyer at the time we were granted a 5 year extension to our family visa even though they had just officially finalized their divorce. This visa will expire in 2020 and I have been told by a solicitor that it may not even be valid at this moment. Would it be possible for my mother and I or perhaps just me now that I am an adult to seek residence in the UK on the basis of retained right of residence? My former step father still resides in the UK and has provided me with documents that show his tax calculations for the years 2012-2017 and would probably give me more documents if requested.
Summary of details:

-Came to the UK with a tourist visa in December 2007 with Brazilian mother and Portuguese step father.
-Acquired a visa of a family member of an EEA national 6 months after arrival and began school in the UK
-Has now lived in the UK for over years 10 years with the visa mentioned above
-Mother was married to Portuguese citizen from 2007 to 2015
-The three of us lived together in the same home from 2007 to 2014
-I am currently employed and live on my own

I would be grateful for your help and please do let me know if I missed any information.