Andrew Cherlin, a sociologist at Johns Hopkins, telephone calls these “capstone relationships.” “The capstone could be the final brick you spend place to establish an arch,” Dr. Cherlin stated. “Marriage were the first task up. Nowadays it is often the final.

Andrew Cherlin, a sociologist at Johns Hopkins, telephone calls these “capstone relationships.” “The capstone could be the final brick you spend place to establish an arch,” Dr. Cherlin stated. “Marriage were the first task up. Nowadays it is often the final. “For...