Do you believe in people seeing ghost?

Would you believe if a friend told you he can see ghost, and pointed it out to you? One of my friends says my baby sister has a ghost who she plays with. When we were at the mall my friend pointed at the ghost and my baby sister walked over where he pointed at. This is not the only time. He also sees spirits and go after him. We went to sweet hollow road once and almost got killed. Also he has told me there us someone staring at me in the back yard which I believe cause when he was never herebu would feel like someone is staring at me. Sooo would you guys believe it or not?