He proposed to a girl, but his father died not approving of her and his mother does not want her

I graduated from university and am working in the field of computers. Then I told my father that I want to marry a particular girl who I am sure is of good character, but my father refused because my older brother had married a girl without his consent then there were problems, so my father is afraid that the same thing may happen again. 
So he told me to marry my cousin (daughter of my paternal uncle), but I refused. He said, if you do not marry her then I will not give you an apartment, so I agreed, but that did not happen. 
Then I wanted to marry a neighbour’s daughter who is 17 years old and comes from a respectable and religious family, but my father, after agreeing at first, refused. I asked him why, and he did not give me a reason, and he said that they are not suitable people and the girl’s grandfather was a mean man. I asked my brothers to speak to my father about this girl, but that did not work. My father died one week later. Now five months have passed since my father’s death, and I want to propose marriage to this girl when one year has passed since his death. But my mother is refusing and saying “Your father did not agree to this.” 
Please advise me, may Allaah reward you, should I propose marriage to this girl or not?