Remember: the past does not equal the future.
That is a famous saying of Tony Robbins, if you've ever come across him?
It's a horrible thing, losing your mom like that, and the grief is heartbreaking.
I imagine, due to the mental pain of the grief, your mind is preparing itself for future trauma, as a means of a defence mechanism. So your brain is building this 'image' up as a means of a defense against any future 'attacks'.
You're likely never going to be truely over what happened in regards to your mother, and so your mind is still fortifying itself. And, as this is near the anniversary of her death, it is something that has been on your mind more than usual, naturally.
But remember, that your father and brother are more than likely going to be fine for the foreseeable future. The past does not equal the future.
I'm not a qualified mental health professional, so take my response with a pinch of salt, but if you feel like its getting worse to a point where talking openly about it with your father and brother doesn't help - I would then suggest you seek professional help, just to put you at ease.
Anyway, take care and I hope that helps.