You didn't post what you found from the IRS. If there is only one child who can be claimed as a qualifying child, the only parent who can file as Head of Household is the parent who the child lived with more than half the year. If there are two children and one lives with one parent more than half the year and the other lives with the other parent more than half the year, then each parent would have a qualifying child and might be able to file as Head of Household.
