This has been discussed many time before. It depend on 1) the age of emancipation in the state, usually 18 but some states are different, and 2) the child DOB.
If the 6 months living with the parent has passed before the date of emancipation then the divorced or separated parents rules are in affect because one parent did have "custody" more then 6 months.
But if the emancipation date is before 6 months passed then custody ends and nobody had custody more than 6 months.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
