I found out my wife and my best friend had a physical relationship before we got married, I don't know how to react

I would go to counselling with your wife.
I can understand why your wife slept with your best friend. She’d had her heart broken & was devastated- and just 18. When you got back together - she felt she couldn’t tell you about it - because as she’s stated - she didn’t want to lose you.
Does your best friend’s wife know about it all?
I’m just wondering why your friend would tell you now?
Ask him - as he’s your best friend.
if you’re all so close - maybe the 4 of you get together & have a big chat about it all.
Also …I’m keep thinking about how much time your families spend together - once a week & more - wow!!! That’s intense !

Oh the irony!

I think you missed this from OP..
“During that time, I was constantly telling my best friend that I still loved her and wanted her back. He would say things to me and give me advice, but now I've found out that, all that time, he was sleeping with her.”

No, I haven't missed the point. I really wouldn't care. I completely see why a pair of kids might not tell in the circumstances and a bit of heartbroken/selfish teenage fumbling back when S Club 7 were reaching for the stars means so little in comparison to a long, happy, fruitful marriage that it would take me very little time to stop caring. If I was just young and foolish when I dumped him, they were just young and foolish too. I'd be more annoyed that he suddenly told me a million years later.

As it is, the whole thing is likely bullshit, in our current established tradition of new male posters joining to tell us terrible stories about their wives and then call us Man Haters (TM) for not doing what they want (centre a largely female space on men). I thought men had serious problems to worry about: male mental health and suicide, prostate cancer, that kind of thing, but no: a website geared around mostly middle aged women is what some of them really can't stand.

I would feel just like you, OP. I wonder why your friend told you now. Did he tell your wife he was going to tell you?

She didn't do anything wrong. You were not together. Yes they should have mentioned it at the time but unless you think there's been some going on for all these years then YABU. Look at it this way. You have a great relationship with both of them by all accounts, your families socialise and both are important to you. Are you going to loose that over something that happened a long time ago that was entirely reasonable at the time? Unless there's something else going on here which you haven't verbalised yet and there may be as his choice to suddenly out himself after all this time is odd. He had no reason to tell.you and should have just kept quiet.

They didn't do anything wrong u just don't like it that they kept the information from you
I would imagine they did it because they didn't want to hurt u because they both love U !
U need to find out WHY he decided now to tell U thou !
That's the strange part in all this
Don't hold it against your wife !

I think this is exactly what's happened.

Asides from the fact that is this a male poster I can honestly say you’re a much cooler wife than me. I don’t for one second care who my DH slept with in his young adulthood prior to meeting me. The upset comes from the assumption that it wasn’t your bf. Why because surely if it’s your bf and person you pledge to spend your life with, it’s a reasonable expectation that they love you and therefore would be truthful with you. It’s not the fact they slept together, it’s the fact they’ve let you assume they didn’t (as most people would assume). That is the hurtful part. That’s how trust works, lying by omission is still lying and when that’s done by your spouse and bf that’s gotta hurt.

You're getting a hard time OP. There'd be very different responses if the roles were reversed.......

How humiliating for you to discover your wife and friend have had a sexual relationship. He's still in your life and all this time they have both known what they did together. You might not have got back with her if you'd known at the time. Does the mother of his children know?

The red flags for me would be....

My wife and he are also very close friends - who stays close friends with a bloke they shagged?

They've always had a very good friendship - They've also had a relationship. They may well have been better friends than partners but they were no longer friends after he got his dick wet.

Our children are all teenagers and are basically like cousins - lets hope they're not siblings.

OP, I wouldn't be able to get past this. You married a woman who is not what she presented herself to be. Your friend has betrayed you. He knew at the time it wasn't right. If there was nothing wrong with it why didn't he share the news with you that he'd met someone......

This won't be popular, but men and women are rarely friends without an attraction in at least one direction. It doesn't mean anything will happen but often men will tolerate friendship in the hopes it becomes more. Men generally don't want or need to be friends with women. They want to have sex with them. Every single male friend I've ever had has eventually tried it on. Not one of my female friends ever has.

I'd kick the pair of them into the long grass. ❤

I think there is a part of this that is the machismo, but she belongs to me, and the fact she did sleep with someone else is at the heart of this.
She didn’t cheat. And even the ‘he shouldn’t have went with his BF ex argument’ can’t be applied here because he knew her long before you.
if she’d told you at the time you would very likely not have got back together with her due to jealousy and this machismo thing. So you can’t be surprised why she omitted it.
He should not have told you because it ultimately is none of your business. They haven’t cheated.

I’m with you op. I couldn’t move on from that. I suspect your friend is harbouring feelings and hoping to ignite something in your marriage.

It's still none of your business. You dumped her, she had a fling, it end a few months before you got back together.
Did you tell her every person you had sex with whilst on your "6 months seperate" presumably you dumped her to play the field

Ok, this is a game changer. BUT it is not worth destroying your family over. The friendship with the other family will probably have to change. Maybe with time you can come back to your friend. But please. Take some deep breaths. Get some personal counselling and then get some couples counselling. To quote Arlo Parks this won’t hurt so much forever … but it is very much NOT worth breaking your dear family up forever over. It’s also ok that it will take some time for you to adjust. Get some counselling. Ultimately your wife didn’t cheat on you, but she does need to understand how deeply hurt you are. Don’t say mean things to each other. She’s your dear wife, you have a happy life and she’s born you 2 (?) beautiful children. Find a way back.

Don't you think it's wrong to sleep with a guy's very recently ex girlfriend when he's your best friend and he's telling you how much he loves her and wants to win her back?

You're kidding right?

She didnt cheat at all you were broken up, im assuming since you done the breaking up you thought the grass was greener else where.

At the end of the day after being with him she still went back to YOU, married YOU, had kids with YOU and according to you have a strong relationship.

Not sure why he told you. Seems bizarre at this late stage - and unnecessary too I feel.

Look, of course it’s going to feel strange. It’s your best friend and your wife and you didn’t see them through this lens until now.

But you are also judging their decisions from that time based on their current ages. They were 18. The decision not to tell you was very much influenced by their age and stage of life then.

It’s weird and it’s changed how you see them as friends. But don’t ruin years of happiness and friendship because of this.

You were all young, at 18 we do things we wouldn’t do as mature adults. We make decisions we wouldn’t make as mature adults. You need to let this go.

Another "there would be very different responses if the roles were reversed ". Do you have any evidence for this or are you another man coming on to complain about women. Plenty of women stay friends with "blokes they have shagged".

I'm far from being a cool wife. But stupid teenage shit from a million years ago just doesn't bother me. I think OP said he dumped her because she said something about his football team? Newsflash, teenagers are idiots. It doesn't have to become a terrible lifelong deal unless you want it to be and I'm surprised how many people want it to be.

Middle aged people have less excuse to act like idiots. If anyone's a villain here it's the best friend who slept with his mate's ex and has now dropped it on him a million years later. But the thread was designed to point fingers at the wife and female posters rather than him. All the endless "WAAAAA, IF IT WAS A MAN...." It was a man! You're just so determined to blame women that you didn't notice and now you're accusing everyone else of being sexist!

It's even easier not to care when there's only about a 20% chance it's true (OP does also seem to have a couple of different personalities) but even if it is... no, stupid historic teenage shit simply doesn't bother me. A person who hasn't changed since they were 18 shouldn't be married anyway.

I agree.

Op, your wife did nothing wrong. I do, however, think your friend was wrong to unburden himself to you about it.

I think I do get this. But like most people here, I wouldn’t be that bothered by it.

In their teens, OP dumped his girlfriend. She was heartbroken. She had a brief relationship with another in her circle of friends, which also ended, then she got back with OP. She took the big decision to trust OP again. Luckily, it worked out well for all of them.

OP is now enraged.

I wonder if this is a male vs female outlook?

She can do whatever she likes when she is single, as can you, as can your best friend.
None of this is as significant as you are claiming. It was a 12 week fling as teenagers. You are being controlling to expect to know every detail of your wife's life
You are being very controlling and acting irrational now. You are making up stories that they have been having sex all along or your kids or not yours. That's irrational behaviour.
You need to grow up, you sound and act like a tennager, no wonder she chose not to tell you if this is how you act

Good lord! I’ve just read all OP’s posts and he sounds totally deranged. I seriously hope he is just a bored teenager making all this up. If it’s true, I am concerned for his wife.

@jhkyg you have to take a breather and think calmly .
You ended it, she had a rebound relationship /fling . A lot of the time it is with someone you are seeking comfort from who is close to you .
She married you. .
She hasn’t been unfaithful .
She could have stayed with him she chose you and they chose friendship.
The secret would be the part I hated . However you wife is correct she was single and it’s her body .
I wouldn’t blow my world apart for this I’d seek my own counselling to address the feelings .
It was just sex when they were teenagers. .

He wasn’t an ex he was her close friend . She found comfort in him when you broke her heart .
They knew that it was sex and went back to being friends.

This! Good lord, what I got up to as a teenager/early 20's was so long ago it barely registers now (also mid 40s)