No, you don't need their permission, and you don't have to tell them what you're doing. Writers the world over base characters on people they know. Sometimes a characters is a combination of several real-life people; sometimes a character starts as a real-life person and then develops into something completely different.
If you're writing what will ultimately be thought of as fiction, you'll find that you have to change "real" events, people, and paces to make them better suit the medium, the story structure, etc. and the end result isn't going to be a mirror on the truth, anyway.
There are risks involved, to be sure: the people you're basing these characters on may see this play at some point, recognize themselves, and then demand answers. There is a balance between telling a story that needs to be told (and you should ask yourself if it NEEDS to be told) and being respectful of the people on whose lives the story is based.
Best of luck. Don't stifle your instincts.
"There are only two tragedies in life: one is not getting what one wants, and the other is getting it." -Oscar Wilde
Updated On: 10/11/05 at 03:44 PM