'Years ago I had a one week fling with my GF's sister and she has no idea.' UPDATED

"Years ago I (38M) had a one week fling with my GF's (29F) sister (35F) and she doesn't know about it. Will everything blow up if I tell her?"

I've started dating my gf last December and I really like her and I love her. Last weekend I was invited to a barbeque on her parents house and met the whole family, and amongst them her sister. When I saw pictures of them both together on Instagram I didn't recognize her because she's changed her hairstyle completely and dresses very differently, but once I met her in person I identified her.

A decade ago I won a prize at work consisting in a whole week of vacation in a touristic place and I met her in the hotel and we connected extremely well on a physical and intimate level and had a great vibe the whole week.

Basically going to the beach, going out at nights and hooking up for six days. We kept contact for a time through Facebook but later on she deleted her profile and we just stopped interacting completely.

When my gf was introducing us I almost froze for a moment, and I could see in her eyes that she also noticed and stuttered a bit but we both acted like we never met before the whole day. I could see her glancing at me at times and I also have absolutely no doubt its her: same name, same voice, same smile, same tattoo.

Must I tell my girlfriend about this? I mean, if I was her, I think I would have wanted to know something like this because it's not like a lonely kiss when we were in high school. But I also think it might hurt her to know and it may also hurt her and that's what I fear the most. I've talked to my best friend about it and he says I should never tell her but I should also talk about it to her sister.

This is what people had to say to OP:

seven-blue said:

Of course you should tell her. If she had the same thing with your brother, you would want to know, right? By not telling her, you are deciding for her. If that is a deal breaker for her, that should be her decision.

You should never go and talk to her sister without your GF. That will ruin things most definitely when her sister tells her you are reaching out to her. Talk to her and be honest. Don't take away her choice about her own life.

mountain_life86 said:

Tell your gf. If she finds out later it will blow up

Zevyn7 said:

It was 14 years ago and yes absolutely you should tell her. Her finding out it way worse

Fendi_1380 said:

Talk to her, don’t talk to her sister. Chances are the sister already told her. You want to make sure she trusts you if she finds out through her sister and not you, then she’ll have reason to doubt you. Obviously it might cause some insecurities but it was so long ago, I think if you say it right, do it in the right way it shouldn’t be an issue

OP responded:

I understand. And should I say it in a casual way, like "oh btw the other day I thought your sister was familiar to me and I remembered later on that I met her once in 2012 during a vacation, etc"?

Or maybe like "listen, you need to know something that happened" and detailed way? I'm terrible at this

The next day, OP shared this update:

Today I had lunch with my girlfriend and gathered the courage to tell her about me and her sister back in the day. I feared that, as some people wisely pointed out, maybe her sister had already told her "Hey, I've met that guy years ago and had something with him, he didn't tell you about it?" but turns out her sister didn't tell her anything.

I tried to just state what happened in the most factual and brief way possible, and that even if she has a couple pictures with her sister on Instagram I didn't recognize her before meeting her in person the other day and she thank God she believed me.

But also I could see how it was progressively affecting her and she ended up crying about the fact that it even happened and it completely broke my heart and made me feel extremely guilty. I know I'm doing the right thing not hiding stuff, of course I understand that, but I'm devastated still over the fact that I'm hurting her so much.

Well she was embarrassed to be crying and wanted to leave the place so I paid, picked up coffee to go and we walked to the harbour and sat there to keep talking in a more solitary place.

She started asking a lot of questions about very specific things like how many times, how it was, if I enjoyed it, if I felt something fer her after that week, how many times had we messaged each other, if intimacy was better with her, and many more things that took me by surprise because I thought that maybe she would want to know the less possible.

And I know I did wrong but I lied and told her I don't really remember that much about those days and that a few days don't really mean anything in my life, that I don't feel and never felt anything for her sister (this is the ABSOLUTE TRUTH) and that it was just a vacation thing that lasted for those days, etc.

She seemed worried about emotional attatchment and I have none, and I'm certain her sister will tell her the same. Idk I felt like a moron and like I hurt her even if unintentionally. Like anything that I could say and do would be a mistake.

Turns out that, to make things worst, the last two years they aren't having a great relationship since her sister divorced and moved back to their parents house and my gf feels like her sister is manipulating their father against her.

So now this kinda hit like a terrible blow and she says her sister possibly expected me to not tell her, so she could keep the info to throw it at her at some point during a fight or anything. I dont really know her sister, so I don't know, but sounds like a very resentful and complicated person to deal with at least at the moment.

It's just so unfair overall, and again, I don't want to make this about me, but I feel like a villain. She said she will eventually talk to her sister but not today because shes too upset, and I think it might be a good decision.

As I was typing this at the office I talked to her again on the phone and she is going to stay in my apartment tonight and I'm glad she accepted, so I'm gonna leave the office early and prepare some nice food for her and try to talk a bit more. Any advice is absolutely welcome and thank you sincerely to the people that guided me here.