Dear Liz: My first husband died when my oldest child was 1. I remarried and had another child (they’re 5 and 3 now). My husband and I prepared a trust in which I have him and my sister as beneficiaries of my assets. But my husband regrets that he is not the only beneficiary.

My argument is that if I pass away and he remarries, I want my oldest son (not his biological son, nor has my husband adopted him yet) to get what I saved for him, and that my sister will make sure this happens. What would you recommend? Should I have him as the only beneficiary?

Answer: No. But your sister probably shouldn’t be a beneficiary either, given your aims.

Any parent who wants to get money to a child should do so with a properly drafted trust, rather than trusting someone else — even another parent — to “do the right thing” by the child. All too often, they don’t. A new spouse, a change in financial circumstances, ill will or basic selfishness can tempt people to justify raiding funds intended for others.

A better way to benefit your children is to set up trusts to receive the money. You can name your husband as the trustee for the younger child and name your sister as the trustee for the elder. Trustees have the legal responsibility to act as fiduciaries, which means they have to put the beneficiaries’ interests first.

You can either create these trusts with your will or they can be part of your living trust if you live in a state with high probate costs, such as California. The advantage of probate is that the court can provide some oversight of the trustee, but that typically involves some additional costs. Your estate-planning attorney can offer guidance about which approach may be best for you.

Dear Liz: My financially illiterate, almost 50-year-old son will be living off his inheritance when I die. A good part of his life was spent drifting, so I have no idea if he will receive Social Security or how much. How do I structure his inheritance so that he won’t fritter it all away in a short time and then expect his dependable sibling to shoulder his burden?

Answer: A spendthrift trust can keep your son from frittering away his inheritance. These trusts limit the beneficiaries’ access to the principal — the amount you put into the trust. This limitation prevents creditors from accessing the principal as well, and he won’t be able to borrow against the trust, either.

That’s the good news. The bad news is that you have to find someone to be the trustee, and that probably shouldn’t be his sibling. Putting one sibling in charge of another’s money is a good way to ensure lifelong enmity. Look instead for a professional trustee at a bank or trust company to fill this role.

A spendthrift trust is not a do-it-yourself project. Hire a good estate-planning attorney with experience in this area. You’ll need to make a lot of decisions, such as how payments will be determined, how often they’ll be made, whether the trustee will have the power to deny payments or to give your son access to the principal if his circumstances change.