I'd be hard-pressed to ever find such a person. The ones you're thinking of didn't stay together for the sake of the kids, they stayed together for some other reason... that's just the excuse they used. Maybe they did it to avoid the scorn of their own parents, or the shame of it (mostly gone in the late 20th century but still found in tiny little pockets, Catholic communities, etc.).

People who were doing it for the sake of the children wouldn't admit it to anyone, for fear that their children might overhear whispered gossip, thus defeating the whole purpose.