No, a stepparent is never obligated to support stepchildren unless the stepparent legally adopts the children. For more information, see Stepparent Adoptions.
Yes. Child support should not be confused with custody and visitation. Every parent has an obligation to support his or her children. With one narrow exception, no state allows a parent to withhold support because of disputes over visitation. The exception? If the custodial parent disappears for a lengthy period so that no visitation is possible, a few courts have ruled that the noncustodial parent's duty to pay child support may be considered temporarily suspended.
No matter what the circumstances, if you believe that your ex is interfering with your visitation rights, the appropriate remedy is to go back to court to have your rights enforced rather than to stop making support payments.
For help with establishing appropriate child support payments -- while balancing taxes, debts, investments, and many other financial considerations -- see Nolo's Essential Guide to Divorce, by Emily Doskow (Nolo).
Parents must support a child until:
Yes. If you're a father with custody, you have the right to ask for child support. Each parent has a duty to support his or her children, and that duty doesn't discriminate between genders.
Anyone who's determined to be a child's parent is responsible for supporting the child. Many unmarried fathers acknowledge paternity by signing a voluntary declaration of paternity at the time of the child's birth or soon thereafter; some are determined to be parents after a paternity suit is filed and genetic testing establishes parentage. It's also possible for a man who never married his child's mother to be presumed to be the father if he welcomes the child into his home and openly holds the child out as his own. For more information, see Paternity Issues and Child Support.