@Anonymous wrote:
who claims him? The parent he lived with more or the parent that supported him more? I have read on many different law sites it is the parent that pays more than half of the support but I cant find the regulation in any IRS publication.
"The parent that pays more than half of the support" applies only to a dependent who is a qualifying relative, not to a qualifying child. But as Hal_Al explained, your stepson is "the qualifying child of another taxpayer" (his mother). Since he is someone's qualifying child, he cannot be a qualifying relative of anyone, including his father or you.
The conclusion is that the mother can claim the son as a dependent, and you and your husband cannot claim him, even if you provide more than half of his support.
