A court is able to order a stepparent to make child support payments depending upon all the circumstances of the situation including the relationship existing between the step-parent and the child. This responsibility exists regardless of whether the separated step-parent has contact with the child.
A stepparent is free to distribute their estate to anyone they wish under their Will. There is no absolute requirement to include step-children in the Will. This said, the step children may be able to apply to the courts for a family provision order if in the court’s opinion the step-parent fails to give an adequate gift to the step child. This is made more likely if the step-parent has benefited from the estate of the previously deceased natural parent.
A step child who has not been adopted by a stepparent will not be entitled to anything if the stepparent dies intestate (that is, without a will).