Perhaps he is going through a tough time right now, and he is reacting, instead of being a family participant. I know what it's like to be the only female in the house. I once had a family of four, myself. In my own struggles, I found that keeping my temper in check, was always good. When you say you have to repeat things, I did that with both boys, (e.g., please take out the garbage), until I thought I was going to pull my hair out. I don't think it is because your are a stepmother, by the way. Finally, I resolved that one by placing the garbage can in his bedroom, until he "got the message." There is no telling if you sit down and have a talk with him, whether or not he will open up. It will depend on his personality. So, if he's not carrying his weight around the house, ask God for guidance and strength to "say the right thing," tell him you are no longer going to 'repeat' yourself, and that there will be some type of consequences for his not carrying his part of the responsibilities around the house. I don't know if he drives, but I've hidden keys until the chores are done.
May God bless you in your endeavor.