So what's his expectation here?
Does he think rejecting this child is more likely to make you forgive him?
If so, why?
I can only assume it's because he is also expecting you to collude in keeping this secret.
The problem is that it's 2024 and not 1924. With social media and "fun" genetic testing in the form of ancestry kits the chances that your children will find out eventually that they have a half sibling is highly probable.
They then face a prospect that both parents have collaborated to keep this information from them. Do you want his actions to rebound on you and your relationship with your children in this way?
Or they are told they have a half sibling their father has disowned and that even knowing this you stayed with him. Growing up knowing you are "discardable" (do it to one child you can do it to another) by your father and your mother still "backed" him is also a recipe for a dysfunctional parent/child relationship.
So whatever he wants he can't put the cat back in the bag (or the cock in its trousers).
He doesn't have to have 2 families but he does have 4 children.
So options that don't utterly fuck up your kids any more than the havoc he's already inflicted:
- you stay together but he takes responsibility for the baby and has joint residency. You would have to accept/agree to becoming this child's step parent and feel able to have a positive relationship with them (and forgive your partner).
- you separate but irrespective of what he wants you do not keep this information from your children (age appropriate). It's then up to him to facilitate contact with the child or deal with the fallout of being a Dad who dumps kids.
What I think you need to prepare for is that unless you take him back and agree to keep the child a secret is that he will leave anyway.
He clearly communicated he doesn't want 2 families.
Right now you and your children are his "first choice preference family".
But if you don't back his plan then you may well be relegated to "disposable family" as he moves forward with OW and the baby.
What would I do?
Tell him I'm thinking things over and need time to process. Act a be pathetic as if I'm not capable of doing anything...while making copies of all financial information (bank accounts/salary info/pensions etc), hiding key documents like passports/birth certificates and engaging a bloody good divorce lawyer.
Seize back control. Be clear I'm not keeping his child a secret from anyone, including your children.
Then expect him to turn nasty and run to OW but be totally prepared for that and glad that he's not your problem anymore.