While more often than not women outlive men and sometimes by many years. In about 10% - 20% of cases, Mom dies first and Dad ends up alone. We see instances of women moving in together after Dad dies for companionship and to share expenses. Men are just not that adaptable. And, what could be worse are men in very traditional marriages where the man does not even know how to boil an egg or do laundry. Wealthy men no doubt will hire full time help to take care of them if needed. But that is not typical. So then what.
First, wives or partners while they are alive must teach their traditional husbands, or partners how to be more self reliant. Cooking a meal once in a while, doing laundry and grocery shopping should be part of Living Alone 101. Doing everything for your typical middle class husband, or partner is doing him no favors.
Next, families need to do the what if's. What if Mom dies and leaves Dad alone? What if Dad dies and leaves Mom alone?. The answer to these questions could be very different depending on age, circumstances, financial condition etc. Moving into assisted living senior communities only works for people with assets, insurance, or nothing so government pays for it. Otherwise, it may be necessary for a remaining parent to move in with one of the siblings. It could be about money and or about necessary care.
Ironically, dealing with Dad will probably be more difficult than dealing with Mom if the times comes. The notion of the Golden Boys is just not as typical as the notion of the Golden Girls. Men don't bond the way women do. In general, Men are more difficult and resistant to change. I know this is a generalization and maybe a stereo type; but I suspect it is more true than not.