There really isn't much you can do, in that whatever you give to your daughter, once it comes to her (once she receives the money or property or whatever), is hers to do with as she likes: she can give it to him, spend it on him, etc.You can establish a trust for her, which will tightly control the money, only spending it for, for example (you determine the rules for the trust) for her health, or to prevent homelessness, and maybe also doles a little extra out each month to her for her discretionary use, but that's the best you can do: limit how much she gets at any time, so she cannot spend it on him. Remember: once it's in her hands, it's hers to use, invest, spend, give away or waste. So you can exercise some degree of control, but only by limiting what she gets, when.If you want to explore the option of a trust as described above, consult with a trusts and estates attorney.