[step-] comb form [ME, fr. OE steop-; akin to OHG stiof- step-, OE astepan to deprive, bereave]: related by virtue of a remarriage (as of a parent) and not by blood "stepparent" "stepsister"
STEP-
Meaning of STEP- in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012