If I am not mistaken I think it is fourteen in Texas
Only if no custody order exist. see links below
yes. you came under joint custody when you turned fourteen.
A 14 year old should be able to choose which parent they live with within reason. This of course depends on whether or not there is a custody case in progress.
At fourteen, most judges will consider the child's wishes when making the custody determination. However, the child's wishes will not override concerns about the parent's ability to provide an appropriate environment and appropriate care for the child, should the court have those concerns.
In this case it does not really matter who have custody since a minor is not allowed to choose and you have to be 18 to do so and by then you are free to live with whoever you choose.
Legally minors are not allowed to choose.
Generally no. A change in custody must be made by a court order.
You yourself cannot choose to move in and live with your aunt. However, if your parents and aunt agree that you should, then you can. If they can't agree and you, as a child, are endangered in your parent's custody, then a court will decide where you will live and who your legal guardian will be.
see related question