First you hide in their closet with the doors closed, then when they get into bed after like 30 minutes make a weird noise. Don't laugh or anything. They will think that something is in their closet. Keep going for a long time. or until they find you.
Worked on my sister! she cried after words though! But, It was funny!
Also, Before you do a prank make sure you tell your family what you are doing so that they can play along.