Where expert evidence establishes parental alienation and that children are in psychological crisis, the court as upper guardian has a duty to urgently intervene by changing primary residence, even where this causes short-term distress, if the alternative is that children will suffer long-term psychological harm and complete alienation from a parent. The best interests of the child principle (section 28(2) of the Constitution and sections 7, 9, and 10 of the Children's Act) is paramount and requires a flexible, fact-based inquiry that is not bound by procedural formalism. A parent's consistent failure to cooperate with court-appointed experts and the Family Advocate, combined with conduct that embroils children in adult conflicts and financial disputes, demonstrates a lack of insight into children's needs and may justify a change in primary residence. Expert psychological evidence based on proper methodology, comprehensive assessment, and logical reasoning will be accepted by the court in determining what serves the best interests of children, absent contrary expert evidence.