Is this a philosophical question or are you asking if this is how it works in our system. Well the answer is victims do not decide the terms of punishment one receives. A victim is able to address the court and give a victim impact statement but the truth is by the time a victim gives that statement the sentence has already been agreed upon by the judge and the prosecutor. Most crimes have a standard range and the facts of the case will determine where the sentence falls on that range.
Generally, victims do not decide the punishment that a convicted defendant receives.
However, some District Attorneys consult with a victim and his or her family. This consultation may be to let the victim and other know the prosecution's view of the case and what the possible out come may be. The consultation may also be to see what the victim and family want to happen to the defendant if convicted. The consultation with the victim and family may be to discuss a resolution the DA would propose to save the family the trauma of trial. If the case is one where the prosecution is seeking the death penalty, family members are frequently called as witnesses for the prosecution.
So, the bottom line answer is that victims and their family members do not choose the punishment; but, depending on events in specific cases, may have an input as to what a sentence should be.
It is understandable that a victim's family would want to determine what happens to a perpetrator.
However, we live in a society where the punishment for crimes is determined by law. Judges can consider the impact of a crime on the family, but they are also required to impose sentences that are fair and consistent with the law.