I have a family member that has two kids in Puerto Rico; which is part of the US. However in PR they don't pay Federal taxes they just fill out the 1040PR to pay for social security.
This family member is the main financial support for his kids, since his ex doesn't work. Now he moved to Florida around Oct 2017, and he brought his kids with him for one month. Afterwards he had to return them to his ex since she has the custody.
Can he claim the tax credit for them even though they only spent 1 month with him in FL?
If so, for how long can he say that they were dependent on him?
The entire year or the period of time in which they were in FL with him?
Their main residence is in PR which is a US territory, but there are some tax nuances, so we're not sure.