My ex has custody of our 14-year-old son who wants to come live with me, what can I do?
In order to do this you will have to go back to court and request a modification of the existing custody order.
Typically, a minor child cannot choose which parent they want to live with. The court will look to many factors - home environment, income and education of the parents, the child's relationship with each parent, reason for wanting the change, etc.
However, while a child cannot outright choose where they want to live, if they over the age of 12, a child's preference is given consideration and is one of the factors that the court considers (the older the child, the more weight it is given).