Is There Something Following My Little Sister?

My family and I have been living in our current house for 5 years now. Ever since we moved in things have been strange especially in our garage. There is an entrance to our garage directly from our kitchen which is connected to our living and dining area. There are no walls that divide each individual area besides the hallway which leads to the three bedrooms one bath. I want to give a general description so people can average out the area I am describing, relatively small house.

Everyone in our house so far has experienced "strange/odd" noises. There are times when we hear people talking in the living room, kitchen especially garage. We hear things getting moved around in the garage. There was one time when my little sisters play kitchen turned on by itself when no one was home, keep in mind they haven't played with it in years. There are no batteries; my mother likes to keep it for memories. My sisters and I have come to the conclusion that there is a possibility that a spirit might be there perhaps of a little girl. My bathroom is located in the garage, and in the shower we can hear talking coming from the garage and kitchen. Being in the garage alone makes us feel like we are being watched. We have never experienced any sort of "activity" in any other place in our house until recently.

This is where I need advice. I have a younger sister. She is currently 17. It's been a few weeks now that we have been hearing/seeing her in different places of the house or even in the street when she is not around. There have been times I can clearly hear her speaking, when I look she is not home. I have seen her on the street, and when I call she is home. My father has claimed to have heard her talking to him, when she isn't even around. There are times when she will spend the night in my room and I notice that's when things get weird. It's the middle of the night and I can hear the keyboard just lightly being tapped. Not hard strokes just light taps as if someone was playing with the keyboard. She claims that I have slept talked to her and there are noises as if they are moving things around in my room. It's been happening more and more often, and I don't know if it has anything to do with her. She's beginning to get scared and so are we. At first we didn't think much of it, but since we have all been hearing and seeing her I'm starting to wonder if it has something to do with whatever might be in our house.

My cousin is currently living with us from Texas and has experienced the exact same thing. Before she moved in we did not tell her anything about what we had experienced, since we didn't want to scare her. She asked us about the noises and seeing my little sister. Keep in mind that my sister is 17, alive and well.

I have never had this happen to me. I don't know what to do. I really need advice. Is there someone I should call? Do I just let it continue? I hope there is someone out there that can take my story serious and give me there opinion. I would greatly appreciate it.