yes they do. it is possible. And unless you are going to lock everybody up for life, you have to accept that people will be released at some point. Rehabilitation in prison will help to reduce the liklihood of that criminal reoffending. Is it perfect? No, of course not, but it can help.
It is the responsibility of the justice system to protect society from those who wish to harm others in that society, hopefully before they commit a crime, but at least after they commit a crime. Are you really saying that a justice system shouldn't try to rehabilitate anybody in their prisons on the basis that 'people don't change'?
I have no doubt that the victim of their family will never be able to think of the offender as anything other than a rapist, and I have no doubt that the release of the offender would be another terrible, terrible trauma for them.
However, I don't think that alone is enough to keep a person in prison if qualified psychologists (or similar people) have come to a conclusion that the criminal is no longer a danger to society.
Note - with crimes like rape, and particularly paedophilia, where the issue of whether or not it is a 'sickness' that the criminal themself cannot control, I am in favour of keeping them in prison possible indefinitely.
My first concern is to protect society, but I believe that rehabilitation is a way to do that.