Some middle-aged couples have grown apart yet continue to live together, a situation sometimes referred to as

The correct answer is married singles.

Married singles refer to middle-aged married couples who have drifted apart due to marital dissatisfaction and / or other reasons, but still continue living together. Such couples almost live separate lives and have a barely existent romantic and sexual relationship. Married singles generally avoid getting separated or divorced in order to protect their children from the negative effects of having separated parents.