Mother Knows Best?
Not in this case. Mother ought to know better than to murder a family member. But how did we figure it out? Firstly, we know that the victim and the youngest are not the same gender. Also, the witness and the murderer’s assistant are also not the same genders.
Since the murderer was not the youngest, we are able to work out that the youngest was in fact a witness. And since we know the father is the oldest, it must mean that the youngest is the daughter. That is definitely one complicated family that nobody wants to invite to a dinner party any time soon!