Heirs betting on their parents’ golden nest eggs are running into harsh demographic realities. Longevity and a slew of changes that have transformed family relationships (ex-spouses, step-kids, step-grand kids, siblings living thousands of miles apart) are turning the already-prickly matter of inheritances into a gargantuan challenge.

Add the gaping generational divide between Depression-era parents, who valued frugality above all else, and their Baby Boomer children, who relish self-reward, and the dynamics can be explosive.

“I see families who never talk to each other again,” says Kotzer, a Canadian lawyer who has written several books, with law partner Barry Fish, on fighting over estates (the latest is Where There’s an Inheritance…). “Family to me is our greatest asset, and we are losing family. …It’s the savers vs. the spenders.”

People are living longer. Health care costs for the frailest seniors are eating up family estates. Their reliance on others to feed and care for them and their finances can put more elderly at risk of financial or physical abuse by the caretakers they depend on.

The shaky economy adds to the volatility as more adult children lose their jobs and see their retirement savings and home equities dwindle while debts mount.

Despite the downturn, more than $20 trillion will be transferred to heirs in the next 50 years — the largest transfer of wealth in U.S. history, according to the Center on Wealth and Philanthropy at Boston College.

“Boomers took risks, and they have a high lifestyle,” Kotzer says. “The housing market went down. The (stock) market went down. A lot of these Boomers have been laid off. Where’s the money coming from?”  the prospect of an inheritance stirs a cauldron of emotions — not always heartwarming.

Eileen Zenker, director of client services at SeniorBridge, a national care management company, says it’s common for children who are faced with costly care for their parents to react this way: “I’m watching my inheritance go down the drain.”

And parents who are in their second marriage have another worry. They need to make sure their children and not their stepchildren inherit their assets. Family feuds over inheritance are as old as the Bible (Jacob tricked his twin brother Esau out of his birthright and their father’s blessing.), and they can multiply in blended families.

There are ex-wives and ex-husbands, children and stepchildren, parents and stepparents. More than half of all first marriages end in divorce and about 75% of divorced people will marry again, according to the National Step family Resource Center. About 65% of these unions will include children from previous marriages. More than 40% of American adults have at least one step-relative, according to a Pew Research Center study earlier this year.