Fathers of young children were historically at a disadvantage in seeking custody of their children due to tender years doctrine—a theory courts adopted in the belief that children had a greater need for the love and care of their mothers during their tender years. Under the tender years doctrine, custody of young children was automatically given to the mother unless there were unusual circumstances. Today, courts more often recognize the important role both parents play in the lives of young children, and usually order some form of shared custody arrangement. But there are factors the court may consider that sometimes favor one parent over the other in determining who will be the primary custodian of the children—such as giving preference to a parent who has not been working outside the home, and has therefore been spending more time taking care of the children’s daily needs.

In Washington State, the tender years doctrine, which favored mothers in child custody cases, is no longer a legal standard. Instead, Washington courts focus on the best interests of the child when making custody decisions, as outlined in RCW 26.09.187 and RCW 26.09.191. These statutes require courts to consider various factors without preference to the mother or father, ensuring that both parents are evaluated on equal footing. Factors include the relative strength, nature, and stability of the child's relationship with each parent; each parent's past and potential future performance of parenting functions; the child's emotional needs and developmental level; the child's relationship with siblings and other significant adults, as well as involvement with his or her physical surroundings, school, or other significant activities; and the wishes of the parents and the wishes of a child who is sufficiently mature to express reasoned and independent preferences. While the court may consider the amount of time a parent has spent with the child, this is just one of many factors and does not automatically determine custody. Shared custody arrangements are common, but the specifics of each case can lead to a primary custodian being named based on the child's best interests.