They could, by arguing they have a legitimate interest in the property. That’s why making a professional Will is so important.
A court could order the title disgorged if your family member can show they had an agreement or contract with the title holder to transfer the property, or part of it, to them. Selling the property can create a constructive trust if the seller would be “unjustly enriched” by doing so.
For instance, a divorcing couple was awarded a 75% share in a father’s acreage after building a home, and paying the property taxes, insurance, and maintenance on it for over 30 years. The divorcing couple was ordered by the court to sell the property, give 25% to the father’s estate, and split the balance (Tomek v Zabukovec, 2020 ONSC 2930).
While the couple lacked evidence they had an oral contract with the father to inherit, the judge was sympathetic that they had invested time, energy, and financial resources in the land on the understanding they would.