The op potentially having been ow IS relevant because that is a different dynamic and does affect everyone's emotions inc the children. I'm guessing msvestibule you've not been a cuckolded partner/spouse it's bloody hurtful and tricky to know what's best - plus people are human they can't always separate emotions out so easily we're not Vulcans!
That said I've had to deal with this situation when the new partner WAS the ow. Eventually (ex played right silly buggers over the whole mess inc lying that dds now stepmum didn't want to) I met with her and put my daughters needs first. I actually like her as does dd. Shame her father didn't handle it sensibly and initially had dd in a horrible position of lying to me that she'd not met ow at the age of THREE! That distressed her greatly.
BUT what I'll also say is - you are only getting your partners version of the story here - you've no idea what he's said to her and his kids about everything. So often the ex is blamed and vilified and then it transpires the truth is not as it seems.
My ex has claimed variously that
1 I wouldn't let dd meet her (not true I merely wanted to discuss and plan how she would be introduced into dds life so dd wasn't upset and confused)
2 That I wouldn't let him see dd at all (again not true, just he kept turning up several hours late or not at all with no communication or drunk/hungover. I just wanted him to behave like a reasonable human being)
3 that she wasn't the other woman, that he and I were already not only separated and divorcing and he was only staying in the house in the spare room to help with dd until I found somewhere else to live (we were in military housing, if all that was true he'd easily have got a barracks room). The reality? We were discussing child no 2 and making financial arrangements inc wills and looking to buy a house near his parents for when he retired which was DECADES down the line, we're going to rent it out in the meantime. It was only when we met that she discovered the truth, to be fair to her she was very apologetic and I think quite shocked. She did however also say that her mum had said to her this was probably the case and she dismissed her mums opinion. I later (much later) discovered that her mum had pulled my ex aside for "a word" and made it clear she knew EXACTLY what kind of man he was. Unfortunately this hasn't protected her daughter at all.
4 The best one - when she was pregnant with their SECOND she (understandably) was keen to get on and get married (they were supposedly unofficially engaged) and he told her it was ME delaying the divorce. I got a text from her that wasn't nasty but expressed her frustration. I provided evidence to her it was HIM delaying signing crucial documents and returning them, they were signed and returned within 10 days after almost 2 years of me/my solicitor chasing him.
"He took a while telling her about the relationship because he knew how she would react and he was right" another way of looking at this is exactly what I meant by "you don't know what her side is" - the decent thing to do would have been to tell her as soon as he knew you guys were serious and then maybe she WOULDN'T have reacted the way she did. One minute as far as she knows he's still single - the next it's he's got a serious relationship and is having another child! That's a lot to take in. Explains the "new woman" thing too.
"she will be dealing with the fall out of that being sprung on her children too." Exactly - children are generally naturally likely to try and please especially absent parents, they may seem as if they're fine to him/you - she may be hearing all their fears/concerns "does daddy still love us?" "Will he still have time for us when the new baby comes?" And that's not without foundation either as I've seen it not only with dd but other families too. Dad loses interest as new family becomes a priority.
"unfortunately she didn't take well to them going home and telling her what a great time they had and how nice I am"
Did she know her children were meeting you? From that comment it sounds like she didn't. Or was the first she knew the children mentioning it to her? Meaning he didn't think to properly co-parent and discuss a new relationship in THEIR children's lives? So she could be prepared for any questions/concerns the CHILDREN may have had (however lovely you are) And before anyone jumps on the "would you tell your ex you had a new man?" I would and did - he was a knob about it but the point is I talked to him before introducing dd to new person.
"whether she still holds a torch for DP or not." Men come and go, but my dd is not to be trifled with. It may be jealousy but as I've said far more likely to be parenting concerns.
"Is he one of those lazy types that is very happy to do bare minimum parenting and blame it on the mother for being controlling?" Yep had this too, ex would forget to change dds nappy, to feed her... But my expectations were too high hmmm
"He was the one who ended the relationship because they had grown apart after almost a decade of being together. They took one another for granted, got comfortable and slowly fell out of love (at least he did)." Again - you only have his word. Nobody outside a relationship really knows what went on within one.
Also have to agree "good father" based on what? He doesn't see them outside hers much, he isn't discussing matters regarding his changed circumstances properly, hasn't considered the effect all this has on the children... Yea great father!
"He was bringing them here when he had them until she kicked off and said no more." BECAUSE he had been less than honest about the situation he was putting the CHILDREN in!
"pays for their keep" does he ACTUALLY pay 50% of what it costs to raise them or csa MINIMUM?
"but if CSA demanded more he would pay it." See above - csa amount is the MINIMUM he should be paying! £450 - the amount means nothing to us as we don't know what he earns, csa calculate as a percentage of his income, what percentage of his income is this?
"Why are you believing all his crap?" Yea I'm thinking same. Reading between the lines it's entirely possible ex booted him for being a lazy gaming obsessed thoughtless twat!
"You know what actually OP, in your shoes I would do nothing. I wouldn’t encourage him to see his kids or stand up to his ex. I would step right back and watch and see what he actually does when left to his own devices. That’ll tell you all you need to know. Do you think he will sort out the contact on his own without you mentioning it? (He won’t)" excellent advice - he'll show his true colours then.
"He has terrible judgement. Which means I take with a massive pinch of salt anythinghe says." Exactly, the ex is understandably angry because he is handling everything SO badly, not keeping her informed of major changes that affect THEIR children.
"Well he sounds far more worried about how things will impact on him than about the welfare of anyone around him." Definitely!
DO NOT call her as per maisypops post terrible advice.
"No. He never wants to upset his applecart!" Precisely
Yes also entirely possible he was still either sleeping with her or giving her the impression he was wanting to get back together at some point. Even if she didn't want to it would still mean that your relationship would have been a huge shock!
"so that wasn't a biggie or unsettling for them" you CANNOT possibly know that you don't know them nearly well enough, nor how the split was managed (or not).
"Ahhh! Poor pet. Imagine not getting enough sleep as a parent.
" ugh yes precisely my thoughts. When my ex was seeing my dd he'd never have her if she had so much as a sniffle, he'd also not have her if he had ANY kind of extra duty in the week before, even if it was on the Monday. Meanwhile I was a full time student, part time employee and single mum with no other support and I'd barely call what little he did support!
"Even before I came on the scene he wasnt getting overnight access. Only ever in the days." Again - HE says - you can't know if this is true. This is another claim not only my ex but several friends ex's have made when I know the very opposite has actually been true, the mum's (in one case a single dad) would have LOVED a break, a chance for a lie in.
Also agree with donnyandvlad very easy for him to lie about contact.
I too think it suits him fine, he gets to play the hard done by wonderful dad while actually doing sod all!
Oh wow! So it's possible his children don't even KNOW they've a new sibling on the way? The 7 year old at least is likely to have been able to suss what the situation was, would quite possibly have been worried sick for all sorts of reasons that is a DISGUSTING position to put a young child in. Not your place to tell them BUT in your position I would not have been around those children while visibly pregnant without knowing they and his ex had properly been prepared and informed. It leaves you wide open to all sorts of awkward questions.
My dd is almost 17 and is STILL trying to get her head around the mess her dad has made of his relationship with her and consequently her relationship with her half siblings.
Geez the phone on silent when you are this far along is utterly unacceptable, actually it's unacceptable at any stage of pregnancy in my opinion.
He has put you in an impossible position without taking responsibility for ANY of his actions (and NOT telling his ex or kids about you earlier WAS an action WAS a choice).
I have to say I agree with ensuring you are protected financially and legally and also prepare for the high possibility of the two of you splitting. I can't see this situation ending well, if for no other reason than you have very different approaches, you value honesty and openness he would rather lie than face a difficult conversation.