Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
In the absence of your father, your brother can represent you and give your hand in marriage. If you are an adult, you may choose either your stepfather or brother or anyone else to represent you.
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
In the absence of your father, your brother can represent you and give your hand in marriage. If you are an adult, you may choose either your stepfather or brother or anyone else to represent you.
Marriage in Islam is a partnership between a man and a woman based on free choice. The role of a wali role is to guide you in your selection so that you don’t err because of your lack of experience.
So as long as you have chosen someone compatible (with good faith and character), you have a right to marry him. You may ask your stepfather or brother to represent you if your father is nowhere in the picture.
Almighty Allah knows best.
Source: www.askthescholar.com