A study published in the Washington University Law Review reveals that appointing one child to control a family trust while siblings or other relatives also stand to benefit is a primary driver of bitter inheritance battles. Examining 640 contested trust cases from San Francisco Superior Court civil filings between 2014 and 2020, researchers found that this specific arrangement frequently combines ordinary sibling rivalry with a deep power imbalance, sparking lengthy and expensive litigation.
Power Imbalances and Sibling Rivalries in Trust Disputes
Nearly a quarter of the reviewed trust disputes involved one descendant beneficiary suing another descendant beneficiary who also served as a trustee. According to Christopher Ryan, a professor at the Indiana University Maurer School of Law and one of the study’s co-authors, giving a single child privileges such as discretion over trust distributions can intensify preexisting perceptions that a parent played favorites among their children.
The research team—which also included Reid Weisbord of Rutgers Law School and David Horton of the University of California, Davis, School of Law—noted that almost all of the contested petitions involved revocable trusts. While these legal instruments are commonly deployed to bypass the time and expense of probate, they frequently trap families in prolonged court battles. Across the dataset, the average dispute spanned 481 days, even factoring in cases that ultimately settled.
Allegations of Misconduct and Financial Scrutiny
Trustees faced direct accusations of misconduct in 74% of the examined petitions, with breaches of the duty of care or loyalty cited most frequently. Nearly a third of all petitions included requests for a detailed accounting of trust finances. David Horton observed that these financial demands typically reflect beneficiaries who strongly suspect their trustees are mismanaging funds or siphoning money improperly.
However, researchers emphasized that many of these legal conflicts are fueled more by emotion than pure monetary gain. As an illustration, Horton pointed to the prolonged litigation involving the Mar siblings, whose case drained their trust’s entire cash assets over a period exceeding five years. The dispute began after their father, Raymond Mar—who died in 2016—granted his son the right to live rent-free in the family home for life, which subsequently triggered a bitter disagreement over whether the son could take in a tenant. In 2024, a presiding judge criticized both sides for excessive litigation and ordered the trust dissolved alongside the sale of the house. Despite that ruling, Raymond Mar’s daughters filed motions in October 2025 to deduct accumulated attorney fees directly from their brother’s share of the trust.
The Cost of Rejecting Settlement and the Value of Mediation
Litigants who allowed their emotional grievances to prevent settlement fared significantly worse in court. The study established that a petitioner’s odds of winning or reaching a settlement dropped by 48 percentage points if their case required a formal trial rather than a resolution based on written filings and oral arguments before a judge. David Horton noted that petitioners driven by emotional imperatives are far less likely to compromise or recognize objective flaws in their legal arguments.
While the exact percentage remains difficult to pinpoint because about a third of petitions quietly disappeared from the court docket without a formal ruling on the merits, the study estimated that up to three-quarters of all petitions ultimately resulted in settlements. Mediation proved particularly effective in resolving these conflicts, with 85% of cases that utilized mediation ending in a settlement, compared to just 47% of cases that bypassed it.
Proactive Estate Planning Strategies
To mitigate the risk of explosive family litigation, the study’s authors recommended that parents tackle difficult estate-planning conversations with their loved ones while they are still alive. Christopher Ryan suggested that explaining inheritance choices proactively can help flush out underlying conflicts before death triggers intense emotional reactions. The authors also advised families to consider appointing an independent or professional fiduciary rather than burdening a family member with trustee responsibilities.
Researchers also cautioned against relying too heavily on legal drafting alone to prevent courtroom battles. Christopher Ryan warned that provisions such as no-contest clauses—which attempt to disinherit beneficiaries who mount legal challenges—depend heavily on state law and cannot guarantee immunity from conflict. Consequently, the authors advised families to plan for potential disputes rather than assuming standard legal clauses will entirely eliminate them.
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