I haven't gotten over my brother's death, is it normal?

Each person heals at their own rate. Your parents are old and have experienced loss in other ways which helped them to heal, though no one ever "gets over" the death of a child. Give yourself time and don't worry about how long it is taking. But let life back in. Go be with friends and allow yourself to laugh or whatever. In time, it will come

You just need more time than your parents. Not everyone is the same. First you have to except your brother has died. Than you can move on to the next stage.

http://postdoos.blogspot.ie/2016/02/how-to-deal-with-loss-of-loved-one.html

Denial won't help. He's really gone. Adjust.

time will heal you