My son and his girlfriend had a child in August of 2012. They had a place of their own, lived with me for a while and lived with her parents for a few months. Early January 2013, they have split up.
In 2012, his girlfriend did not have any income and her parents did not provide more than 50% of support for their grandchild. My son even took $8K out of his 401K to help provide for his son.

Now, his girlfriend is telling my son that he can't claim my grandson on his income tax and that either her or her parents are going to claim the child.

1) Is this legal?
2) If it is legal, does my son have any claim to the tax return that is directly related to the child credit?

I'm just trying to figure out all the options for my son (and any advice) and if I need to get an attorney involved.

Thank you.