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Forget taxes. Your relatives are the ones who'll get in the way of your windfall from your rich aunt.
A poll by TD Wealth showed that 44 percent of attorneys, trust officers and accountants cited family conflicts as the biggest threat to estate planning.
TD Wealth surveyed 109 estate planning professionals earlier this year at the 52nd Annual Heckerling Institute on Estate Planning in Orlando, Florida.
It turns out modern families create more estate planning complications.
"We see more blended families, multiple ex-spouses, kids from prior marriages and situations where one spouse is much younger than the other," said Ray Radigan, head of private trust at TD Wealth. "These fact patterns can pose problems."
>Here's how to keep the peace between your family members, while ensuring your loved ones get a fair slice of the pie. 
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The only way to ensure that assets are divided the way you would like them to be is to draft an estate plan.
Individuals who die intestate — that is, without a will — leave everything up to the state in which they reside.
"In New York, if you die without a will and leave behind a spouse and kids, your spouse gets $50,000 plus half of the balance, and what's left is split evenly between the children," said Radigan.
Indeed, there are situations where a 50-50 split between beneficiaries may seem fair on paper but aren't in reality.
Let's say that a married couple runs a family business, and it makes up the majority of their wealth. One of their three adult children is actively involved in that business, but the other two aren't.
In this case, the business owners can opt to purchase life insurance to help make the two less-involved children whole, or they could give them a nonmanaging interest in the business, Radigan said.
"Treating them fairly might be different from treating them equally," said Radigan. "Minimizing the estate taxes is the easy part, but the hard part is the family dynamics."
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Don't leave your family members in the dark about your estate plans, keeping your arrangements a surprise until your death.
Instead, clue your beneficiaries in on the how and why of your estate plan, said Radigan.
For instance, beneficiaries who are receiving their distribution in a trust for their benefit might interpret that as a punitive move that creates an obstacle between them and their inheritance.
Instead, tell your children what you're hoping to accomplish with your estate plan.
"When you create a trust, you're not punishing your kids — you're protecting them," Radigan said.
"This way, they have access to the funds when it's appropriate, and when the money is in the trust, it's beyond the reach of court claims," he said.
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It's easy to put your estate plan on the back burner, especially since the Tax Cuts and Jobs Act raised the estate tax exemption to $11.2 million per person.
Now is the time to take a second look at your will, trust documents, beneficiary designations and, if applicable, business succession plan.
"There are two events that might trigger a review of an estate plan: New tax legislation and a change in your family situation — a birth, a death, a marriage or a divorce," Radigan said.
This is especially important for baby boomers: The divorce rate for those age 50 and older has doubled between 1990 and 2015: out of every 1,000 married people, 10 got divorced, according to the Pew Research Center.
"A lot of the kids are millennials and they actively participate in the family," said Radigan. "They would be resentful if they didn't hear what was going on with mom and dad's estate plan."
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