Confidants are your loyal wives and an added source power as they boost retainers.
There are two main stats to look for in a confidant: Intimacy and Charm.
Intimacy: Affects the Attributes of your offspring. Higher intimacy grants more attributes. Intimacy is also used during the Intimacy events.
Charm: Affects the amount of EXP obtained by confidants when summoning or cherishing. The EXP is used to level the confidants skill, in which will boost the attributes of the retainer.