I live in N.J. And am wondering when the legal age for a child to decide which parent he or she would like to live with.

The child cannot "decide" who to live with, however the court will take the child's wishes into consideration. The court has the responsibility to place the child in the most stable home.

The child can not decide, if the parent who does not have custody wants the child, they will have to file in court for custody, Then the child can testify in court, and the parent who wants the child, shows the court it is in the child's best interest.

The current parent with custody of course has the right to try and prove this would not be a good idea.