1) Adopter, sometimes 2) Parent 1) Stepfather 2) Stepmother 
• (n.) Stepfather or stepmother.
Step'par`ent noun Stepfather or stepmother. 
The spouse of a parent, who becomes the stepparent of that parent's child upon marriage. Stepparents are not legal parents of their spouse's children unless they complete a stepparent adoption, which requires the consent of the other legal parent or the termination of that parent's rights. (See also: stepparent adoption)
[n] - the spouse of your parent by a subsequent marriage
noun the spouse of your parent by a subsequent marriage
a stepfather or stepmother.