I assume that the child is not related to you. A "godchild" relationship is not considered related.
He/she may be a “qualifying relative” dependent if:
…He/she is not filing a joint return with anyone else
.…He/she does not file a tax return claiming someone else as a dependent
…He/she is no one else's qualifying child
…He/she lived in your home as a member of your household for the entire year.
…His/her gross income was $4,000 or less (2015). Social Security benefits that are not taxable do not count against this limit.
…You provided more than 1/2 his/her support for the year.
…Your living relationship did not violate local law.
…He/she is a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico, for some part of the year.
