One Monday evening there was a murder in the home of a married couple, murderer who had two children, one son and one daughter.

One of the others one of the members of the family witnessed the crime.

The other one helped the murderer.

These are the things are know for sure:

1). The witness and the killer were not of the gender.

2). The oldest person and the witness were not the same gender.

3). The youngest person and the victim were not of the same sex.

4). The one who helped the murderer were older than the victim.

5). The father was the oldest member of the family.

6). The murderer was not the youngest member of the family.

Who is the murderer? And who was murdered?