Can I Be Forced To Change My Last Name?

Can I be forced to change my last name? When I was 5 my mother remarried. My stepfather adopted me and my last name changed to his. Since then my mother and stepfather divorced, he remarried. Now his new wife is stating they want too summons me to court and force me to chnage my last name back too my biological father`s name. I don`t want too. I am 27 years old, I plan on marrying my fiance in a year, then I will change my name. Legally can they force me too before then?