Haunted House

I'm pretty sure our house is haunted (not Bryan and Mine.. but Mom and Dads). This weekend mom and dad went away so Bryan and I had it all to ourselves.. Well whenever i'm home alone over the past years I always hear noices and it always sounds like someone is upstairs walking around. But there never is and no one ever believes me. Well Friday Bryan and I were in our room and Crystal came over so it was only us three in the basement. Then at the same time we all hear someone else ... it sounded like they just came in and had like bags and keys. So we went upstairs thinking mom and dad maybe came back. But sure enough there was no one. But we all heard it. Then later that week Bryan and I kept hearing someone upstairs.. even though the door had been locked all weekend, and ever time we went and checked no one was there. It was pretty creepy. Then it happened Monday morning after Bryan left for school. At about 7:30 I heard someone upstairs.. but no one else was home. It was creepy. So i've decided mom and dads house is haunted.