The kid at camp

In the mid to late 1970s, my parents were in a camping club, with about 5 or 6 other couples, and camped at various campgrounds together around the Midwest (we are from Chicago). One time we went to this campground that had a little park near a large pond with a playground not far from the water. My sister and I were playing in a sandbox (I was around 10 and she was a couple years younger) having already gone on the swings and see-saw earlier. Suddenly out of nowhere this boy who was probably about 12 or 13 wearing a black t shirt with a rock band logo on it and bell bottom jeans with patches on the knees was standing in the sandbox a few feet from us. He had curly black hair down to his shoulders and dark eyes. He didn't say anything for a couple seconds and my sister and I looked at him nervously as he wasn't smiling and staring down at us.

"Are you brother and sister?" he finally asked. I told him we were. "Are you camping here?" I also said yes. "Where is your camper?" I stupidly without thinking told him the section of the campground my parents club was camping in, which was about 2 blocks away. "Do you guys know who the Johnsons are?" he asked the name of one of the couples camping in our parent's club. I said yes. "They're my aunt and uncle, I'm going to surprise them later that I'm here." He went on to say he was camping with his dad and he gestured vaguely in a direction on the other side of the pond.

The kid squatted down close to my sister. She backed up in the sand closer to me. "You guys look so alike, you can definitely tell you are related." he said, which was kind of ironic, since I'm adopted and my sister is my parents' natural child. We did both have brown hair and eyes in common. "Did you guys want to come to my camp? My dad brought tons of snacks with, I can give you marshmallows to roast if you want." I told him my parents already had marshmallows. "Well we have graham crackers and Hershey's bars too, you can make smores. I'll give you some of them to take back to your camp." I lied and said we have them too, as tempting as smores sounded.

My younger sister finally said she needed to go to the bathroom which I took as my cue to get away from this weird kid who was really starting to make me feel uncomfortable even at that young age. "We're going to go now, we'll see you later when you come to your aunt and uncle's." I told him. He didn't get up when we got up but instead leaned closer to us. "There are bathrooms right down that road," pointing again past the pond, "by where our camper is. You can take her there and then stop by and get some candy from my dad." I told him there's a bathroom right over by the main office which was just across the street from the playground, we'll just use that one.

Suddenly the boy jumped up, kicked whatever my sister and I had been building in the sand, and jumped out of the sandbox. "You are so dumb, who turns down free candy? That's okay, more for me then!" My sister and I rushed over to the office building, and I was fearful that he'd follow us there, but after a few seconds of staring at us, he turned around a began to run down the path towards the other side of the pond. I took my sister into the men's room, she did her thing and we cautiously looked around for the boy who was nowhere to be seen before we hurried back to our campsite. Once there, I told my parents about what happened, and the Johnsons happened to be sitting on the picnic table having coffee with them and we told them it was their nephew, who was going to surprise them. Of course, they said they didn't have a nephew but were a bit weirded out that someone knew who they were. My sister and I stayed at the campsite the remainder of our time there, and of course the creepy kid never did come to our campsite.

EDIT; I used the name Johnson for the name of the people in my parents' camping club because I can't remember their real name.

EDIT 2: I now remember the campground was one of those that had a big Yogi Bear statue with a huge picnic basket when you first drive in but can't recall where it was, maybe Wisconsin?