IPA: /ˈstɛpˌpɛrənt/
KK: /ˈstɛpˌpɛrənt/
A person who is married to one of your parents but is not your biological parent.
My stepparent is very supportive and caring.
Stepparent is formed from "step" (from Old English "stæpe", meaning a step or degree of relationship) and "parent" (from Latin "parens", meaning a father or mother). The term refers to a person who is a parent by marriage rather than by blood, indicating a step in the familial relationship.
Think of 'step' as a degree of relationship and 'parent' as a mother or father — a stepparent is someone who takes a step into the role of a parent.
No commonly confused words.