How does the daughter-in-law feel about that? "She doesn't know," Arzaga says. Nor does her husband.

While sometimes in-laws are left out of the will because the patriarch wants the wealth to remain in the family, other times it's because the parents fear the in-law's profession or spending habits will leave their child open to creditor claims. Clint A. Costa, an estate attorney with Harrison & Held LLP in Chicago, says he has a client whose daughter-in-law is an
obstetrician/gynecologist. Given the high cost of medical malpractice insurance, she doesn't carry as much coverage as the parents would like, so they put their son's inheritance into a trust and made the trustee an unaffiliated third party. If the daughter-in-law is sued, creditors can't make a claim on the inheritance, given that the daughter-in-law has no interest in it.
"OB/GYNs carry huge medical malpractice issues. The parents probably wouldn't have been as worried if the daughter-in-law was in family practice," Costa says.

One of the most common vehicles used for protecting the family wealth from an in-law is a qualified terminable interest property trust, or Qtip, which allows the children to get the income generated by the family assets, while the assets themselves go to the grandchildren. The child can be named as a trustee to govern everyday investment decisions, but he or she wouldn't necessarily have total control because an independent third party can be named as co-trustee with veto power on all major distributions. That way, should the in-law want $100,000 to start a new business, it would not be solely up to the spouse to release the money. The independent co-trustee would first have to determine whether the distribution was appropriate.

Asher says he often helps his clients cut their children's spouses out of the will, but he doesn't always think it's the right thing to do-particularly when the child is in a good, healthy marriage, and the in-law helped provide for the family or raised the children. Rightly or wrongly, in-laws expect that when their spouse receives an inheritance it will go toward the marital unit, just like any other kind of income the spouse might receive.

"Maybe it's greedy for the spouse to expect that, or to resent the change in lifestyle that will happen when they don't get it, but when it's been a long marriage, and there were no issues or distrust, where the spouse is considered a daughter or son, I personally believe they should be able to share the inheritance," Asher says.

Putting Marriages At Risk
Also, cutting out the in-laws out of fear that a couple could split can be a self-fulfilling prophecy. It's not likely to break up a good marriage, but it can certainly cause tension, particularly when parents require their children to obtain pre- or post-nuptial agreements, estate planners note.

"I guess they don't trust their own kids' judgment," says George Cassar Jr., an estate attorney in Southfield, Mich. "But we've definitely seen situations where forcing the kids to obtain a pre- or post-nup agreement caused the relationship between the son and the daughter-in-law and the parents to fall apart."

Cassar says he had one client, a successful doctor from Pakistan, who wanted his son to marry a Pakistani woman, but the son refused and married an American. The father was so displeased that when he helped the children buy a house, he refused to allow the daughter's name to be put on the deed. His feelings about the daughter-in-law caused so much friction that she severely restricted how often the grandparents could visit their grandchildren. These days, that's about once or twice a year, even though the grandparents live just 20 minutes away.

"We get a lot of this, especially in the Arabic and Indian communities," Cassar says. "They want their children to marry in their culture. And if they don't, the older generations get pretty upset."

Keeping a child's inheritance away from his or her spouse is not always easy. Once assets are used for marital expenses, like a house, or food or a child's tuition, they are considered to have been commingled and thus become marital assets, meaning the in-law may get half of them in the case of a divorce.