Lost my dad to a brain tumour when I was 22 so I know exactly what you are going through..
You will feel a whole range of emotions, numb at first, devastated later, and guilty over enjoying anything for a while and along with that huge hole in your life, you are in for a rough time.
Just get through it however you can and remember that is what families are for, take all the help you can as it will be bad once this really sinks in.
And please, look after your mum, she will be lost for a while, and being around will help her so much as she will facing all sorts of hell and will need you and your brother more than you realise.
You dad may be gone, but he still lives through you and your brother, you are both half him if you get my meaning, be proud of that, as it will be a comfort to you in the dark days ahead..
Our condolences to you all..