AITA for wanting my step-son to pay me rent.

Me: 42F, mother of 2 from another relationship (d17, m14) <br><br>Partner: 42M & son J18<br><br>To begin with: <br>I never wanted to be a mother - I regret giving birth<br><br>It was an unwanted pregnancy. I was young, stupid and made a mistake. I decided to give birth and give the child up for adoption. I wanted to be a closed adoption, where the child would never know me or anything about my identity. I wanted a clean cut and no contact with the child. <br><br>A few years ago, my son contacted me. I was terrified. I never wanted this, and I did not want contact with my biological child. My son is not happy that I did not want him, and that I wanted to give him up for adoption. He wanted to have a relationship with me and I refused. As a result I have a strained relationship with my biological son. <br><br>I met my current partner a year ago and we moved in together a few months ago. My children live with us as well, and my partner's son is with us as well for the time being (more below). <br><br>My children have to do chores, this includes cooking a few times a week, cleaning, taking out the trash, recycling and gardening. My youngest has to clean his brother's room and my eldest has to take care of our 2 cats. As they have been taught to do chores, my partner's son is required to do them as well. <br><br>My partner's son is spoiled and lazy. He does not do these chores and he believes he doesn't have to do them. He has messed up my eldest's room by opening drawers and stealing from my daughter. She had around 350$ stolen by her brother over the last few weeks. The Police were called and my partner's son was arrested on the spot. <br><br>I want him to pay back the money he stole. He does not have a job, but he gets 1600$ a month in student aid (for University). I believe that he should pay back my daughter what she lost. Which is around 600$. My partner's son refuses to pay back the money and has thrown a tantrum. He believes that he doesn't owe her anything and that I am unfair. As a result, I have told him that he needs to pay rent in the future. He never contributed to the household before and he never does his chores. So it is unfair that he can steal money from my daughter and I am unfair for asking him to pay it back. As a result, I have told him that I will charge him 700$ a month in rent. <br><br>My partner's son refuses to pay and he told me that this is ridiculous. I told him that he can either pay the 600$ back first and pay the 700$ a month in rent. Or he can move out. I will not have him living under my roof for free and stealing from my children. <br><br>He refuses to pay and I am not willing to back down. My partner believes that this is too harsh. He believes that I should be willing to forgive his son for stealing because he has apologised. I refuse and he has told me that I am overreacting.<br><br><br>Update:<br><br>Both of my children are happy that their step-brother is moving out and so am I. <br><br>I have been told that he has found a job and has accepted my terms. He has paid back my daughter and has paid the 700$ in rent. However, he has told me that he will be moving out in 3 months. <br><br>It is what it is.