To feel uncomfortable with this message exchange

Yes but we're not talking about you. Have you not read the messages shared in the exchange?

Is tone and content the same as you would use with your platonic male friends?

The only reason that they haven't got together before is that she is probably out of his league and she has always had somebody else. Your partner has obviously fancied her for years and thinks that he might get her on the rebound. Honestly, he's coming across like one of those eager Labradors with their tongues hanging out.

Yes, you snooped but who wouldn't in your situation. Those messages crossed the line. And now, he plans to leave his pregnant partner and go to London this weekend to "party" with the poor sad depressed gorgeous mite. Anybody who thinks this isn't the start of an affair must be a Pollyanna and/or utterly naïve.

To be honest, depending on how pregnant you are, I'd terminate the pregnancy and dump him. Failing that, I'd be telling him that it was either her or me and there would be no going to London to "party with her" and she needs to seek professional help. I can't think of a single scenario where this would be acceptable behaviour. And as for your family disliking him, I suspect it might be more than the fact that he doesn't earn much. He has demonstrated startling disloyalty. It doesn't look like he gave you and the baby a second thought other than to criticise your family when he saw there might be the possibility of sex with her. And as for cloning him, one faithless disloyal man like this is more than enough.

YANBU
You are being too reasonable.
Partying in London with her after those texts?
You need to have a long calm chat with him about boundaries.

Would two best hetro friends talk like this? A little blurry on two hetro women as most my girl friends build each other up and aren't shy to say something along the lines of I'd take you home... But most hetro men would never talk to each other like this... I'm sorry @Notjustmeah you aren't overreacting

You're not overreacting at all at their flirting. I'm afraid something may well happen when they meet up. I'd let him know you know, but not sure it'll stop it.

One of you? OMG, yes, please... I need you now ... groaned breathy Angelina Jolie.

Nothing inappropriate at all 🙄

Let's be honest, that's exactly how her messages sound to him.
And let's be honest - she knows how to construct a suggestive sequence of words.
If she really is stunningly attractive, she won't be doing this to start a relationship. However, sex for a bit of fun and distraction is not at all excluded (very likely, I'd say). DP is hook and sinker up for it.

That⬆️ last sentence is all there is to say, figuratively and literally.

Reads to me like he’s seeing an opportunity and is trying his luck.

The ‘find a clone of me’ is fishing imo - he’s trying to gauge how receptive she is to him without outright propositioning her, and also planting a seed in her head (‘Look how good a guy I am, right in front of you for all these years. Given that you can’t have a clone of me, how about me instead?’).

That they haven’t got together in the past isn’t necessarily because he hasn’t wanted to.

I'm all for having friendships of the opposite sex as a couple, I see nothing wrong. I have always done it and encouraged my partners too but those messages cross the line. Looks like your husband has some sort of infatuation with skinny blond and she is heart broken and in need of some hugs. I would sit with him and have a chat, tell him he's making you feel uncomfortable, do not accept any form of gaslighting. He needs to stop making you feel uncomfortable, plus you're about to have a baby. Do not mention the phone snooping.

Try to exclude her is making it into a battle. This is his pal - making her into yours relegates her to "family friend" instead of potential rival

I'm hoping he came to his senses and didn't go.

This is bonkers advice. Bring her even closer into the relationship she’s already intruding into?!

They seem to have been testing out if the other is attracted to them and each has made it clear that they’d be interested in the other. Red flags all over this. If he wants to carry on with messages like this he needs to be single so it’s time to confront him while there’s still hope that he’ll come to his senses. The only way he can prove he can be trusted now is if he’s willing to totally cut contact with her and focus on you and the baby. Unfortunately, too many affairs start like this: people testing out other potential partners, it escalating, and all while being too cowardly to end existing relationships in case they change their mind about the exciting new option and end up blowing it all.

@Notjustmeah, this is totally unacceptable. Your P is choosing to play with fire and shit all over your relationship and family.

The dynamic between them has shifted, as they have absolutely started an emotional affair. They sound intoxicated by their KISA/Damsel intimacy, which is being energized by their physical attraction. They’re building a romantic connection.

Act now, @Notjustmeah, or you will bitterly regret not doing so. If my H had been uttering those words and pouring an abundance of his emotional energy, time and attention into another woman, I would be reading him the riot act and investigating my options. He would certainly not be going to party with her, and cutting her off completely would be a requirement before I would even consider continuing our relationship.

Yeah, it's bang out of order. ''Id give all the money in the world for a guy like you'?? Or whatever. It's nauseating teenage sounding absolute gagger flirting.
Who says that to their platonic friend.
Tell him to go out with her.
You deserve a faithful, respectful partner who doesn't act like a cock end.
No doubt whatsoever she's not going to be exclusively dating him if they do 'get together'.

One of my best friends is male and yes I have whinged about my husband and in-laws at times, just as I do with female friends.

However, in over 30 years of friendship we have never messaged like that - they’ve crossed a line, the feckin idiots.

This would hurt me so much, I couldn’t unsee it neither could I imagine trusting him ever again and would not be comfortable issuing an ultimatum.
my only option would be to let him go.
fuck them, pair of arseholes

Helpful. OP can’t reverse the pregnancy can she!

My DP (now DH) had a drop dead, gorgeous, rich, ex who kept in touch. I made friends with her. (We did lose touch, but only because she moved away) If you are still fit enough, invite yourself along. Perhaps, you could discuss her coming to the christening, and if wedding is in the discussion, ask her to be a bridesmaid. This puts her firmly in your circle, and you can drop her later.

Sorry OP, this would be completely unacceptable for me.

I have no issue with platonic male / female relationships but in my view those messages amount to cheating. Totally unacceptable. And how pregnant are you OP? Why is he leaving his pregnant partner alone to go and 'party' with her for the weekend? This all seems quite off to me.

Have you discussed her situation with him and said now she is single and you are pregnant you would feel much more comfortable if he didn't party with a single woman due to putting himself in a position that could compromise your relationship.

This

I think going to party with her is off with you being pregnant, i would go with him , but i would say words to those for a friend to lift up their spirits in reply to the messages. you need to be in their company and feel the vibe in their presence.
If it is going to happen it will regardless.
I don't worry myself due to that way in my thinking.
Have you discussed her situation with him and said now she is single and you are pregnant you would feel much more comfortable if he didn't party with a single woman due to putting himself in a position that could compromise your relationship.

Emotional cheating. You both need to create solid and strong boundaries when it comes to opposite sex friends. This is way over the line and needs to stop immediately. My partner just told a women he looked hot in a shirt and they both bashed me. He is no longer friends with her because I was devastated by their inappropriate relationship. There's some good videos on YouTube about what these boundaries could look like.

So he’s texting his ‘friend’ sympathising and they both think guys who cheat are arseholes. But this is really his chat up line to fuel his emotional affair and get his ‘friend’ to blow smoke up his arse. Cloning and fawning.

And they both think he is the good guy. A man who is worth cloning. Wow.

There’s some twisty cheater logic going on there. I regularly say cheaters tie themselves in knots to justify their behaviour. These two are pretzels.

Read ‘Not just friends’ by Shirley Glass.

I wish you well. This is all him, not you. The only prize here is you. Cheating is a choice and he has crossed many boundaries here.

Did he go to London?