It all depends how the mom will raise the kids. There are kids that will kill thier parents all for insurance, tis been happenning every time. I would rather be alone and old in the Retirement house than living with kids that you know will slit your with just one signal from their mother.
You know what makes hell for a family? Its the in-laws.
If you are going to raise a kid who is not going to bother about killing their parents just to get money then the parents are to be blamed.People rarely do the things as you said for some hate towards their parents basically due to the sex abuses in their childhood.
It's not always the fault of the parents. Children can have genetic inclinations to violence. Some kids are born with psychopathic tendencies and if parent's don't notice it early those tendencies will continue to develop. It is partially the fault of the parents but the kid doesn't have to be abused or neglected to become a murderer.