A study examining 640 contested trust cases has identified the estate-planning decisions most prone to sparking conflicts among heirs. The research, published in the Washington University Law Review, reviewed civil court filings from San Francisco Superior Court between 2014 and 2020, revealing how family wealth often becomes entangled in legal disputes.
Granting a single heir control frequently leads to disputes
The most frequent source of conflict involved designating one descendant as both trustee and beneficiary. In nearly a quarter of cases, a beneficiary sued another beneficiary who also served as trustee—typically a sibling or grandchild. Indiana University law professor Christopher Ryan and the study’s authors described this arrangement as a key factor in creating disputes. Nearly all of the petitions involved revocable trusts, a common tool to allow a successor trustee to manage the settlor’s property long after their death.
When one child gains authority over trust distributions, sibling rivalries often intensify, Ryan observed. Such arrangements amplify ordinary family tensions by introducing a power imbalance. For instance, a parent granting one heir special privileges, such as allowing them to live rent-free in a family home, can provoke resentment among others. In one case, the Mar siblings engaged in five years of litigation over whether a brother could sublet the inherited home.
Raymond Mar, who died in 2016, had given his son the right to live rent-free in his home for the rest of his life. By the time a judge dissolved the trust and ordered the house sold in 2024, its financial reserves had been depleted. Despite the ruling, Raymond Mar’s daughters filed in October 2025 to deduct attorney fees from their brother’s share of the trust.
Read Also: White House publishes guest list for Trump-Xi dinner
The study found that in 74% of cases a trustee was accused of misconduct, often specifically breach of duty of care or loyalty. In nearly a third of petitions, beneficiaries requested a detailed accounting of the trust’s finances, which Horton said reflects beneficiaries who suspected their trustees were mismanaging funds or ripping them off.
Many of these fights appeared to be driven more by emotion than money, according to Horton. Petitioners’ odds of winning or reaching a settlement dropped by 48 percentage points if their cases required a formal trial rather than a judge ruling based on filings and oral arguments. David Horton, a UC Davis law professor and co-author, noted that petitioners driven by emotional motives were less likely to reach a compromise.
Most disputes, likely around three-quarters, resolved through settlement, though the exact figure remains uncertain because about one-third were dismissed without a formal decision. Mediation proved significantly more effective, with 85% of mediated cases settling compared to just 47% without it. Even when settled, the average dispute lasted 481 days, showing the delays and costs trusts can impose despite their goal of avoiding probate.
No-contest clauses rarely prevent conflicts
Ryan added that parents cannot rely on provisions that attempt to prevent court battles, such as no-contest clauses, which disinherit beneficiaries who raise legal challenges. However, the study found these provisions rarely succeed. Their impact varies by state, and emotional motivations frequently outweigh financial consequences.