stepsister的复数形式怎么拼写？

She was also going to have a new stepsister.她也将有个新姐姐....

stepsister的音标：stepsister的英式发音音标为：['stepsɪstə(r)]stepsister的美式发音音标为：['stɛpˌsɪstɚ]...

n.（继父与其前妻或继母与其前夫所生的）姐姐，妹妹...