Good afternoon Sam,
I'm Doug, and I'm very sorry to hear of your family's situation. My goal is to provide you with excellent service today.
As long as your son is not deemed an unfit parent by the court because of abuse or neglect of his child----which would be apparent by now---then there is legally no basis for the stepparent to obtain legal custody of your grandchild.
However as you have learned, the CO court does not have jurisdiction over the child because of federal law. Let me explain.
The Uniform Child Custody Jurisdiction And Enforcement Act,("UCCJEA"), dictates that once a parent and their children reside in a given state for 6 months, that state acquires jurisdiction over the children for purposes of resolving all custody issues. That means that any petition for modification of custody must be filed in the state where the children have resided for at least 6 months.
All your son needs do is petition the court ion Co for custody of his son and that custody request will be granted. The stepparent has no chance in gaining custody when your son, the natural father of the child, seeks custody.
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.
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I wish you and yours the best in 2015,