"Sometimes, it's the kids who are the gold diggers," Whitenack said.

After 30 years of practicing law, elder-law attorney Bradley Frigon of Denver said he is seeing more of these contentious relationships. People are living longer, he said, and are more likely to enter into new romances after divorce or the death of a spouse.

"There are a lot of wonderful marriages late in life that work well," Frigon said. "But when the new spouse and the kids are very suspicious of each other, that can cause problems."

The kids may have no legal standing to intervene if the older person has "capacity" -- meaning he or she is of sound enough mind and not suffering from dementia or other incapacitating illness.

"Dad may make some really bad decisions," Whitenack said, "and there's nothing you can do about that if he is an adult and if he is competent."

But whether someone has capacity is not always clear-cut. "Is Dad being eccentric or is he crazy?" is how Champion summarizes this dilemma. And even people who don't have dementia can be subject to "undue influence," where they can't resist the will of a stronger or more controlling person who can successfully pressure them to do things they wouldn't otherwise do.

One thing that probably won't work is being blunt about your suspicions of your parent's new love. "That's like saying to a teenager, 'This person is not good for you. You should stop seeing her,'" Whitenack said. "They're going to get all defensive on you and tell you to butt out."

Instead, try sympathy and a gentle nudge toward an attorney who might help protect the parent's assets. "You can say, 'It must be really great to have someone in your life,'" Whitenack said, and then go on to point out that late-in-life relationships and marriage can affect pensions, Social Security, veterans benefits, taxes and possibly credit obligations. "'Maybe you should connect with an elder-law attorney who can help you take care of things.'"

A prenuptial agreement or a management trust can put assets beyond the reach of a gold digger. Other things that elder-law experts say families can do to battle a financial predator:

  • Do everything you can to stay in touch. Financial predators often try to isolate the elderly person from his or her family, Champion said. The predator may get to the phone first when you call, for example, and make excuses about why your parent can't talk to you. Or she may be so unpleasant in face-to-face encounters that you'll be tempted to stay away. Keep calling and visiting anyway, and include the parent in family gatherings, even if it means accepting the predator's unwanted presence. If you don't live close enough to visit often, consider hiring a geriatric-care manager to look in on your parent every week or so. (You can find information on hiring these specialists on the National Association of Professional Geriatric Care Managers website.) Costs vary widely by the level of service, but they typically range from $20 to $90 an hour.
  • Consider early intervention. Many families feel squeamish about interfering with a parent's romantic or social life, but elder-law attorney Donna Bashaw of Laguna Hills, Calif., said they may need to overcome their reluctance if the parent is suffering from dementia or other cognitive problems. Getting the parent away for a few days on a vacation or trip to see relatives may be enough to destroy the predator's influence if it's still in the beginning stages, Bashaw said. "If it's early, I try to get the families to get (the parent) away from this person," she said. "Sometimes taking a trip is enough to get (the parent) to forget them."

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  • Call for help. If you suspect abuse, neglect or exploitation, the National Center on Elder Abuse recommends calling the elder-abuse hot line in the state where your parent lives. The national Eldercare Locator hot line at 800-677-1116 also can direct you to the protective-services office nearest your parent.
  • If all else fails, consider conservatorship. A conservatorship gives you legal authority over your parent's affairs, but it can be an expensive and sometimes futile battle if the parent fights back. If you believe you may need to go this route, hire an attorney who specializes in this area. The National Academy of Elder Law Attorneys can offer referrals.

Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.