Dave,
When my grandmother passed our family was torn apart by a sibling war over her estate. The estate was partially planned and some legitimate arrangements were made to insure fairness. The only problem was the attitude of the heirs. One in particular, started to bank on the inheritance and therefore made life decisions that assumed a certain dollar amount. The matter complicated by the onset of Alzheimer's disease that made it virtually impossible for my grandmother to make a rational decision. Arranging care and housing in the latter years of her life drained her savings.
Before her death, the court had to settle a dispute over guardianship, the court also ordered her finances to be handled by a book keeper. It was a mess. One of the heirs had to pay money back to the estate...and the bickering resulted in wounds that may never heal in this lifetime.
In any event, I think you can have a water-tight plan, but if heirs have immature attitudes and false expectations, then it really doesn't matter how well you plan. Take Billy Graham for example. His sons and daughters have openly disputed places of burial, legacy issues and so forth.
This verse from Proverbs taught me an important lesson:
"An inheritance gained quickly in the beginning will not be blessed in the end." Proverbs 20:21
I have been named the executor of a couple of estates, and I have to remind myself that my job is not to covet another's belongings in the event they pass. My job is to carry out their will and bless others by exercising prudent judgment.
Relationships are the best investment we make on earth and they yield the highest return. All too often, that ideal gets lost when a loved one passes, especially when they leave behind a significant estate.