TIFU by groping my sister-in-law

For starters: My wife (24f) has an identical twin sister, and I mean identical. Same hair cut and weight within a couple of pounds of each other.

I (23m) went on a beach vacation with my wife, her sister, sisters husband, mother-in-law, and father-in-law. We rented a beach house for the week (Saturday to Saturday), and every morning the family drove a short distance to actually lay out and swim on the beach for a couple of hours. Then we would head back to the house, shower, and everyone would kind of split up and do their own thing the rest of the day. The beach house is on stilts, under the house is enough room to park a couple of vehicles on one side, and the other side has a storage closet and an outdoor shower.

Every morning when we got back from the beach our routine went something like this; women shower first while the men put the cooler, chairs, towels, bags, and boogie boards away in the closet outside. Then the guys usually stand around or raid the fridge until the showers are free after putting everything away.

Every single morning my wife used the outside shower, I was even able to slip in the shower with her on Tuesday when her dad and brother-in-law went inside to wait for their showers.

Friday was our last full day at the beach, everyone was burnt out so to speak, so instead of the usual car load of beach supplies we only took a cooler, couple of chairs, and everyone had a towel. When we returned to the house and I volunteered to put the chairs and cooler up while everyone got showered. Not going to lie, I volunteered so that everyone would scurry inside so I could hop in the shower with my wife. Without getting too vulgar, I’ll just say I was ready to rock-n-roll. While I was putting the stuff in the closet I heard the outside shower cut on, normally I would have ran up to the room to grab a towel and shorts, but I was too worked up. I just decided I would ask my wife to grab them after the shower and bring them down to me. I finished putting everything up and opened the shower door. There she was, back turned, washing her hair; an idea came to me. I quickly dropped my trunks and snuck up behind her, then proceeded to play out my idea. Trying to keep this as PG as possible; I positioned myself behind her so that I could poke her where the sun doesn’t shine, and simultaneously reach around grabbing her boobs, and kiss her neck. It worked, with her eyes closed and washing her hair she never saw it coming. Immediately she turned and slapped the dumb grin off of my face. I didn’t know what was happening, I was holding my face and trying to gather my thoughts. About two seconds passed and she pushed me back as hard as she could and screamed, “Get out of here.” When I heard her voice and saw the anger in her eyes, I knew it wasn’t my wife, it was her identical twin. I turned around, grabbed my trunks, and like a dummy said, “Please don’t tell anyone.” I don’t know that any words would have helped the situation but maybe I should have said something like, “I thought you were my wife.” At this point, with trucks in hand I stepped around to the closet to get covered, I heard the water shut off and she ran upstairs. I wasn’t sure what I should do, but I thought I have to go explain myself.

I opened the door and was met by my brother-in-law and father-in-law. Brother-in-law was being held back by father-in-law, brother-in-law was swinging his arms and acting like he wanted to fight. I said, “I thought it was my wife in the shower, this is a misunderstanding.” Brother-in-law was yelling, “I’m going to stomp your ass, you sick pervert.” Father-in-law says, “I think it’s best if you take a hike.”

I went outside and sat in my car, waiting for my wife. When she came out she was surprisingly understanding. We had a long conversation, I won’t quote it all, but in short she said, “My sister asked if she could use the outside shower, I didn’t think anything of it because I didn’t know you was planning to hop in.”

I wasn’t welcome back in the house, she had to pack our bags and we left Friday mid-day instead of Saturday morning with everyone else.

TL;DR tifu by mistaking my wife’s twin sister for my wife. I walked in on her in the shower, I poked her, grabbed her and kissed her.