There are multiple definitions - click on the translation that matches your context.

step-parent means:

madrasta means:

madrasta

substantivo

partial

step-parent

noun

The term "madrasta" in Portuguese refers only to the stepmother, not to the stepfather.

a stepfather or stepmother (=a father or mother relationship created by someone marrying again)

Blended families, with one step-parent, have been common for years.