Step-Children, Beneficiaries
Just as any other person or entity, a step-child may be named as the beneficiary of a specific gift or of the residuary estate.  The Pennsylvania inheritance tax rate for step-children is equal to the rate for natural and adopted children.

Unlike natural or adopted children, step-children are not entitled to a portion of the decedent's intestate estate.  Not being classified as heirs means that step-children do not have standing to contest a will that omits him or her without showing they would have otherwise benefited in the absence of that will.

See: Step-Children, Disinheriting; Primary Beneficiaries, Generally; Alternate Beneficiaries, Generally