Is my repentance for stealing money from my parents—under duress and threat of publishing my photos—sufficient, or must I repay this money to my family, given that I currently do not possess the money?

We praise Allah Almighty for your repentance and ask Him to grant you steadfastness. The Sharia has made it clear that sincere repentance erases sins and transforms bad deeds into good ones, and Allah loves those who repent. As for a young man threatening you with publishing your pictures to force you to steal your father's money, this is coercion, and coercion absolves you of sin. The Prophet, peace and blessings be upon him, said: "Indeed, Allah has forgiven my nation for mistakes, forgetfulness, and what they are coerced into." Therefore, there is no sin upon you, nor is there any liability for what you stole. The sin and financial responsibility fall upon the one who coerced you, because coercion removes choice and abrogates obligation.