I'm late to the party and have posted this before but this is all true
I have a younger brother who had an imaginary friend when he was younger. He was also an avid sleep walker. When he was around three or four, he started talking to someone he called Friya (Fry-uh). He described Friya as a dark skinned man with little clothes who loved to hunt in the wilderness. Then one day he told me that Friya used to live nearby the house a long time ago. And then some white people came and burned him alive and killed his village. Not exactly something you expect to hear from a four year old. I remember I would be in my room and hear him talking like he was having a conversation and when I would try to check on him, he would immediately become silent and turn his head as soon as I peeked around the corner. Very unsettling. Well my other brother, the middle child, was visiting his dad for the summer but the day before he got back, my youngest brother told my mother and I that "Friya does not like when (brother) is mean to me. He's going to scare him." The night he got home, my mom and I were downstairs and heard a scream that I can still hear to this day. We ran upstairs and found the middle brother swearing that someone was shaking his bed violently. It was a bunk bed. My youngest brother was sound asleep. A month later, my youngest brother took a bad fall and cracked his skull. He was fine, but never talked to Friya again after that. He would also sleep walk constantly. And show up right next to my bed and stare at me until I woke up and promptly shit myself. One night I heard my front door open and close. Since it was 4am, I went to check it out. I opened the door and found my brother at the far end of the yard, in the snow, only in his underwear, staring right at me. Then he slowly waved. Those shivers weren't from the cold.
TL;DR My youngest brother had an imaginary friend who could have been a Native American. Scary stuff ensued.