A couple of nights ago I (19m) was camping with my gf (18) and her family. It was night 1 of our 3 day camping adventure. My gf shared a tent with her mom. I shared a tent with her brother (22). The dad shared a tent with no one. When everyone was supposed to be sleeping, my gf approached my tent and woke me up. She had beginner level stealth mode skills because her brother was wide awake when she was done unzipping our tent. Not the end of the world. My gf and I anticipated that outcome during our brainstorming session at the beginning of the trip. As per our plan, my gf said she had to pee, which was my cue to say "I'll walk with you." This was meant to be the first phase of our secret mission to have sex in the woods without the family knowing.
However, I literally forgot about the secret mission. I never said "I'll walk with you." Instead, I asked the brother if he was keen to come with us because it seemed less ominous to be wandering in the woods in the middle of the night if we were more than 2 people. The brother shrugged and said he might as well pee. My gf stared at me like I made no sense to her. She said if I didn't want to be alone with her, then I was more than welcome to be alone with her brother. I had to exit my tent without being fully dressed because she stormed off without warning. She disappeared. I repeatedly tapped on her tent and whispered "babe" enough times for the person inside the tent to finally respond. It was her dad. I was at the wrong tent. In my defense, it was dark, I was still recovering from a dream I had about being born with teeth growing out of my tongue, and not to mention all our tents looked the same.
The dad asked what I was doing barefoot in my boxers in front of his tent. I said nature was calling and I was looking for someone to keep me company. The dad connected the dots and asked if I was hoping that someone would be his daughter. I had no idea how to respond. The dad nodded as if my awkward silence was an undeniable yes to his question and sarcastically asked if I wanted his daughter to hold my hand or something smaller. Again, I was unable to comment. The dad put on his boots and emerged from his tent with torches and toilet paper. I said I didn't need toilet paper. The dad said it was for him. I peed, the dad pooped. I was forced to shut my eyes and think happy thoughts because the dad sounded like he was puking mud.
On our way back, the dad suggested that I share a tent with him from now on. I was too traumatized to turn him down. The dad and I have been sharing a tent ever since, which made it impossible for my gf and I to have the privacy we planned for. I'm currently not in the best bf category with the gf.
TL:DR My gf and I secretly planned to have sex while we were camping with her parents, but when it was time to execute the plan, I ended up sleeping with her dad instead.