Father: Mid 50s beta bucks. Not in fighting shape, but has held up well for his age. Good head of hair, not fat, and is aesthetically above average. Divorced from first wife, my mother, after ~30 years for about one year now, started divorce two years ago, some of the financial judgments still being appealed and clarified, but 95% complete. Solid six figure job before overtime. When the over time comes, we're talking five figures a week if he wants it. Mid six figure 401k, very healthy pension you don't find these days anymore. Modest house paid for, not worth too much due to location and age of it, maybe 80K. Keeping his retirement after the divorce and paying first spouse a rather modest mid five figure sum for her half of house and furnishings etc.

A very reasonable ruling when looked at objectively, perhaps even in his favor all things considered. The ruling was one he was still not happy with on the basis of his emotional logic that he made approximately twice as much as her the last decade or so and she spent twice as much. Not wealthy outside of retirement funds, income has grown significantly only in the last decade or so. Not terrible with money, but is mostly money in equals money out. Very secure job and little chance for an on the job injury.

His Fiancé: Approx. 50 year old. Big tits, long hair, skinny-ish, but wrinkly and saggy nonetheless. Still hitting that tanning bed she should've given up two or three decades ago. One of those slightly orange people. This will be her third marriage. Unknown first marriage length and circumstances. Second marriage was childless and lasted around 5 years, maybe 5 years ago. Split due to money problems, nothing left to divide up at the end but debt, that he got stuck with. I have seen her 2nd husband around and he has a good job and makes good money for the area. I've heard she was with him for his above average, but not wealthy, money. He's not much to look at.

She has three kids with at least two different men, it may be 3 men. All kids grown, the oldest 2 are decent enough. Youngest is around 20 and though she has her own beta bucks, mommy still gives her whatever extra she asks for. She works for maybe time and a half to two times minimum wage at an hourly job.

Father's Divorce/Split Up: My father's fiancé was one of a handful of similar aged women in a female friend group that would socialize together for a few hours a few times a month. This group included my mother. My mother is my mother, but she is a little bit crazy like all women. By crazy I mean irrational, overly emotional, and solipsistic etc, not Jesus talks to me crazy. I think she decided she wasn't happy and nothing was going to change that but leaving my father around ten years ago. I think she was sort of conditioned by many of her friends and TV to sort of idealize and romanticize getting divorced.

It's clear she had a plan in place, and my father beat her to the punch by about six months on it after discovering enough pieces to the puzzle. I listened to both their bullshit for a brief time after they were splitting up, got tired of it, told them what they needed to hear, and peaced outta there. My father's viewpoint and motivation is much more difficult for me to speculate on during this stage. It was a huge blow to his giant ego.

Post Split Up/Divorce: Father was angry about it all, was a drag to be around, and really just focused on how much money, specifically retirement he was going to lose. Mother just spouted the same self-serving bullshit that sounded like lines from some book on how to be a victim and how to talk to your kids about divorce. I laid down the law with her again. She was receptive to it, and have kept a decent relationship with her after it.

Whenever I tried to tell my father what he needed to hear, he got angry and borderline tells me to get fucked. He just wants to be told what he wants to hear. As far as I can tell he found someone who will tell him what he wants to hear. He turned to that old friend of my mother, his now fiancé, to hear all his bullshit. I'm sure after socializing with my mother, his fiancé was able to hone her swoop at my father and sink her talons deep. In the last year, year and change, he has taken her on at least three vacations. After the first vacation, he just grabbed some clothes from his house and moved in with her.

My siblings and I get together maybe once a month at his house. He is rarely around, though we tell him we are going to be there and his fiancé lives ten minutes away. Post wall pussy must be the shit? /s I might see him for a few hours at Christmas or Thanksgiving at his parents house, or he may stop in for five minutes to say he is engaged a few months after the fact.

The engagement: My siblings and I are in agreement that this is the dumbest shit ever. They're not going to be able to have kids due to her age. She is a few time loser in the marriage game with known money issues. He is entering into an agreement where he can only lose. She will quit fucking him good and treating him right moments after he puts a ring on it. He lucked out once on keeping his retirement. We aren't going to be supporting his ass if he loses his ass due to an avoidable conscious decision. And so on, everyone here knows the game and why this is a bad idea.

Attempts to far: I know a reasonable prenup can stand a good chance in protecting everything he has acquired up to this point in his life, but isn't bullet proof and does shit for what they acquire in marriage. That's fine. He shouldn't marry her, but if he does he shouldn't go full retard. One sibling he notified via text about the engagement texted him back simply saying "prenup." That sibling has yet to hear back from him in any way. I called him and left a message saying he should get a prenup. Saying further, "remember how pissed you were just a year ago about your retirement and the judge and your money etc?" I haven't heard dick back either.

It would have been nice to have been able to tell him, "fuck no, stupid!" before he proposed. When he first started living there, I warned him many times about not getting married.

Question: How can I convince my father to get a valid prenuptial agreement at this point? Has anyone had any luck in protecting someone against themselves in a situation like this? What worked and what didn't? I'll try again, but it looks like I'll need to do better next time.