What about your other parent (own mother)?
You could try registering as a British citizen under Section 3(1) about two-three months before your 18th birthday. It is by no means guaranteed, as it is generally expected that you have lived in the Uk for at least two years. However, if you can prove that your entire family is now resident in the UK and that your future home is in the UK, you may succeed.
See page 27 onwards of the
Registration as a British citizen - children guidance, with especial attention to Pages 29-30.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.