They are and should be allowed to attend and to be heard by the judge/jury. They shouldn't be given a vote, but I think their opinions/wishes should be considered.
I agree with Savvy. It's good for them to be heard, but I don't think voting is a good idea. When they're too close to it, it's hard to give a rational vote versus an emotional one.
Oh, you think rationality is important in a situation like that, I see. Hmm, now that you've brought it up, I'd actually prefer it the other way around.