Lyle Hansen (plaintiff) filed a petition for divorce from Delores Hansen (defendant) after 18 years of marriage and the birth of two children. At all times prior to the filing of the divorce petition, Delores had been the children's primary caregiver. The trial court awarded joint legal custody and joint physical care of the two children to Lyle and Delores, despite evidence that Lyle and Delores rarely communicated civilly or showed mutual respect during the marriage. The trial court established a schedule under which physical care of the children alternated between Lyle and Delores for six-month periods, with liberal visitation granted to the non-custodial parent. Delores appealed, seeking sole primary physical care of the children. The court of appeals reversed the judgment of the trial court and granted exclusive physical care of the children to Delores. The Supreme Court of Iowa granted certiorari.