Should young ever be better off with one parent than with two?

We analyze models of parental care, providing the first systematic comparison of the care given to young by one parent versus by two parents. In the Houston-Davies model of care, young always do better with two parents rather than with one parent. When one parent decides about its level of care before the other, then the young may do better with one parent when the costs of care for the parents are asymmetric. When the level of parental effort is reached by negotiation, there are cases in which young do better with one parent, even when costs are symmetric. The analysis suggests empirical ways to differentiate between different response rules.