Parents are still married after 45 years although they literally cannot stand each other and stay together for the principle. They are absolutely miserable together. This is their second marriage and in my opinion, they should have ended it years ago but that's for another day.
Your parent's are like Abby's aunt and uncle. Miserable in their marriages, and now merely determined to outlive one another out of pure spite. I can't imagine going through life like that.