I'm Doug, and I'm sorry to hear of the confusion. My goal is to provide you with excellent service today.
While there is no age at which a minor in CA may demand to live with one parent as opposed to the other, under CA law the court will give consideration to the minor child's preference as to which parent they want to reside with.
CA Family Code Section 3042 states in pertinent part:
3042. (a) If a child is of sufficient age and capacity to reason so as to form an intelligent preference as to custody or visitation,the court shall consider, and give due weight to, the wishes of the child in making an order granting or modifying custody or visitation.
(b) In addition to the requirements of subdivision (b) of Section 765 of the Evidence Code, the court shall control the examination of a child witness so as to protect the best interests of the child.
(c) If the child is 14 years of age or older and wishes to address the court regarding custody or visitation, the child shall be permitted to do so, unless the court determines that doing so is not in the child's best interests. In that case, the court shall state its reasons for that finding on the record.
(d) Nothing in this section shall be interpreted to prevent a child who is less than 14 years of age from addressing the court regarding custody or visitation, if the court determines that is appropriate pursuant to the child's best interests.
So while the general rule is that children over the age of 14 may express their preference in the event of a custody case, the judge does have the discretion to consider the wishes of a child under the age of 14 as well.
Often the judge will speak with the child in chambers without the parents being present. Given your child's age, it seems unlikely that your ex will be able to persuade the court to consider your son's wishes---even presuming that he is able to brainwash your son.
You may reply back to me using the Reply link and I will be happy to continue to assist you until I am able to address your concerns, to your satisfaction.
I hope that I have been able to fully answer your question. As I am not an employee of JustAnswer, please be so kind as to rate my service to you. That is the only way I am compensated for assisting you. Thank you in advance.
I wish you and yours the best in 2016,