Is a stepparent obligated to pay child support?
Maybe. When determining child support, courts will always look to the child's biological parents first. But a stepparent who lives with his or her stepchildren has a duty to support the children under Washington's family expense statute. A stepparent who does not live with the children (i.e. someone whose spouse has kids from a prior marriage that lives with the other parent) has no support duty.
The stepparent's support duty terminates when the stepchild voluntarily leaves the biological parent's home, when the marriage is dissolved, or when the court otherwise orders it. A stepparent may still be ordered to pay child support while a divorce or legal separation is pending and until it is finalized. Informal legal separation of the parents is not enough to end the stepparent's support duty.
Of course if the stepparent adopts the steppchild, he or she will be considered the same as a biological parent for child support purposes (and almost all other purposes too).
For more information, contact a Kirkland family law attorney.