It seems to be without doubt,your late fathers wishes contained in his will, still stand. Your mother simply has a lifetime interest in the house, during which time, she could sell it, but the proceeds would have to be divided 50/50
between yourself and your brother. However in accordance with your late fathers will, in the ordinary course of events,
your mother has her lifetime interest, but on her death the
house would pass to yourself and your brother 0n a 50/50
basis. Yourself and your brother are known as the "Remainder men".
I am not sure that your brother has been acting properly
as an executor. Therefore it would be very much advisable
to see a Solicitor, in order to protect your interests.