Hide in his closet, but pretending as if you've gone to bed already. And when he goes to his bedroom to sleep himself. Wait until the light is turned off and him being good and comfortable. Then barely open his closet door just a little and begin making strange growling sounds and saying his name in a creepy way. He'll either yell for his parents or hope that he doesn't jump up and kick your but. Lol
A good scary prank to play on your brother is hiding on his bed when is asleep and shouting his name loudly so that he can hear it and tell him that you have been hunting him. Make sure that your voice is strange for him to be scared. Another prank is to pour cold water on him when he is relaxing and pretend that you did it by mistake.
Wear a monster looking mask and get a blanket and drape it over you and when he's going to bed wait about an hour and open his door slowly and close it and stand over him and wake him up and grab his shirt and scream like a demon roaring or scream like a little girl.