In your situation, it seems like you prioritized having your finances and your family life undisrupted over a loving, intimate, and full engaged relationship with your wife.
I do not believe he ever mentioned why they never got married. Maybe he wanted too but she was against it? Maybe they got pregnant early and made the best of it without pulling the marriage/wedding trigger?
If she was the one who never wanted to get married, I bet she's regretting that decision now. The institution of marriage does provide certain protections. It may be somewhat outdated in today's age (which we've had many discussions about here) but his girlfriend is free to be dropped like a bad habit at a drop of the hat especially since the kids seem to be over 18.
I know, Scott, you've written that you want to move on this fast and she's trying to delay it-
You have a daughter's wedding coming up- I'm assuming it's going to be a summer wedding? Have you thought about how that day will unfold? Obviously, it's your daughter's day and her feelings and wishes should be taken into the fullest of account. But do you plan to sit next to your girlfriend during the vows? Have you thought about how you will handle having your daughter and her partner exchanging vows of loyalty and faithfulness (if traditional vows) to each other while sitting next to your unfaithful girlfriend? Could be rather triggering and hard to get through.
Do you plan to dance with your girlfriend after the father/daughter dance? (Again, I'm assuming the norms of a traditional wedding...?) There's a bunch of little things that will occur that will require a pretty exceptional acting performance from both you and your girlfriend. Happy, smiling pictures together? The toasts to the happy couple? I know you will do the best for your daughter but best of luck to you getting through it if you plan to go to the wedding with your girlfriend and continue the charade of a happy, together long-term couple...
Of course, the petty cynical side of me might be tempted to tell the girlfriend you want to act fast and get all this settled before the wedding because you plan to take a date to the wedding. That sort of thing is generally frowned on and will open up all sorts of problems that your daughter would not appreciate at all. But oh!... the temptation would be there...
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