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by JEANNE FLEMING, PH.D. and LEONARD SCHWARZ

Question: I hate to say it, but my son-in-law is no good. Three nights a week he goes out with his buddies, leaving Melissa at home with their toddler. Recently, they asked my husband and me to help them with the down payment on a house. While we would like to help our daughter, we’re sure her marriage will end in divorce, and we would hate to see our hard-earned cash winding up in Josh’s pocket. What should we do?

Our answer: Leave your checkbook in the drawer.

While sabotaging your daughter’s marriage would of course be wrong, being realistic about the likelihood that it will succeed is not. If there is a good chance that this marriage is not going to last, pouring your money into the couple’s joint assets is a bad idea. Not only do you risk having made a very large gift to your selfish son-in-law, but whatever you give them now means you’ll have that much less available with which to assist Melissa should she and Josh split up.

More generally, while helping an adult child with the down payment on a home is a wonderful thing to do, it’s not always the right thing, and it’s by no means an obligation of parenthood. Moreover, under no circumstances are you obligated to give money to a son-in-law you don’t like, especially one whose character concerns you. Since Melissa wants to make this large investment with Josh, that is a decision you must honor. But it is not one you’re required to bankroll. We only hope your daughter’s not imagining that, though having a baby hasn’t kept her husband home at night, having a mortgage will.

Questions? Email Money Magazine’s ethicists – authors of "Isn’t It Their Turn to Pick Up the Check?" (Free Press) – at FlemingandSchwarz@right-thing.net.