Can there be a conditional clause in a will? Is it possible to bequeath something to a person IF they do not do something but, then. Bequeath it to a different person IF the first named beneficiary does something that you object to?

Yes, but it's hard to answer how this could be done without more specifics. Are you concerned about an action the beneficiary might take AFTER you die and the will is probated? Or actions that would occur BEFORE you die? If after your death, is there a time limit you would be willing to settle for? What I'm thinking is that you could set up a trust with income from the trust going to the first beneficiary, but if that person does a specific action that is prohibited, then the income goes to the 2nd beneficiary. This trust would have to have a time limit though - perhaps it expires when the first beneficiary reaches a certain age, then the principal of the trust is distributed to him. You'll have to think through contingencies such as what happens if the 2nd beneficiary "misbehaves" in the same way as the first, or if one (or both) of the beneficiaries dies before the trust expires, or if they have children when they die? You also need to name a trustee to administer this. A big downside of this approach is that it costs money to set up and administer, and in general it is a bad idea to try to control your beneficiaries' actions from beyond the grave - you can never fully account for every possible contingency, and consequentlly your money may not end up where you really intended it to go.

Yes and no, of course it can't be based on something llegal, like you would give them the money if they killed someone. And it has to be something easy to prove, a general issue such as 'live a moral life" is too subject to opinion.

A Will is probated and settled and then it's over - this is a matter to be covered by a trust.

Yes, but it's hard to answer how this could be done without more specifics. Are you concerned about an action the beneficiary might take AFTER you die and the will is probated? Or actions that would occur BEFORE you die? If after your death, is there a time limit you would be willing to settle for? What I'm thinking is that you could set up a trust with income from the trust going to the first beneficiary, but if that person does a specific action that is prohibited, then the income goes to the 2nd beneficiary. This trust would have to have a time limit though - perhaps it expires when the first beneficiary reaches a certain age, then the principal of the trust is distributed to him. You'll have to think through contingencies such as what happens if the 2nd beneficiary "misbehaves" in the same way as the first, or if one (or both) of the beneficiaries dies before the trust expires, or if they have children when they die? You also need to name a trustee to administer this. A big downside of this approach is that it costs money to set up and administer, and in general it is a bad idea to try to control your beneficiaries' actions from beyond the grave - you can never fully account for every possible contingency, and consequentlly your money may not end up where you really intended it to go.

When I die, I would normally bequeath my house to my wife. However, my wife had a secret affair in the past and I would not want my wife's extramarital lover to come back into her life and take up residence in my house. Would it therefore be possible to bequeath my house to my wife only if she never got back together with this other man? Then, would it be possible, if she did ever get back with this other man, for the house, or the proceeds of the sale if the house had been sold, to revert to my children and my wife would forfeit it?
It would be up to the executors of my will to keep tabs on this and to take action if my wife should get back with her ex-lover.

No, it's not possible.

This is called "control from the grave."

And no one (including your Executor) is going to spend the rest of his/her natural life following your wife around to see who she's dating.

So order the house sold when you die and have the proceeds split.

Your best action is to consult an Attorney in your State - you'll need one to write your Will, anyway - and see the best way to handle this.

No, it's not possible.

This is called "control from the grave."

And no one (including your Executor) is going to spend the rest of his/her natural life following your wife around to see who she's dating.

So order the house sold when you die and have the proceeds split.

Your best action is to consult an Attorney in your State - you'll need one to write your Will, anyway - and see the best way to handle this.

Im going to split hairs on this one and say that it may be possible to keep someone else from taking up residence. How it could be done is to will the home to the children directly and state that so long as the mother is alive she may live there rent free so long as she lives alone. The only real problem in what the OP is asking is that it is assumed that the house belongs to him but in fact if it is a community property state then only 1/2 the home belongs to him and the other 1/2 does not. So that being the case you would be forbidden by law to exempt someone from their own property.