Cat peeing & pooping everywhere but her litter box!! Help!!!!

I have a 7 year old Himalayan Sealpint. She is spayed. I'm having major issues with her doing her business in our basement hallway, kitchen floor(even on her food dish!!) closets, rugs, bathmats, you name it, she'll go on it. I have been living in this house for about 2 years, she never did this at my previous house. Also, I know she really dislikes my son, hes 2. Chases her and swats at her :/ We also have recently had my brother in law living with us. These are the only things I can think of that would be her reason for this. 

Other posters have said to try cat attractant on top of your litter. Since you've had your cat for a long while, you must already know to keep her litter box clean by cleaning it at least once a day. From her perspective, life is stressful with a 2-year-old who is not only chasing her around, but also swatting at her. She may be trying to claim her territory as she feels very stressed out over her living situation. Maybe Feliway or Comfort Zone with Feliway plug-ins or other stress relievers may help her. Please try to teach your 2-year-old not to chase or at least not to swat your cat. When my niece was about 1 years old, her mother would constantly say, "Gentle! Gentle!", when she was trying to pet an animal to teach her to stop petting so hard. It worked and she learned. A new person in the house is also very stressful. Maybe he can give her her treats or feed her sometimes if he doesn't already so she will like him if he is part of the problem.