A child's spouse is not classified as an heir according the intestacy laws of any state.  When a child inherits a portion of a parent's intestate estate, the inherited property belongs solely to the child.  The child's ownership is the same as though the parent had given that property to the child while still living.

This sole ownership is not changed by marriage, whether the child is married before or after receiving the property.  Again, just as with property that is received as a gift, the child is not legally obligated to share any portion of that property with his or her spouse.

Even those states that have community or marital property laws generally exclude any property that is inherited by either spouse in an individual capacity from inclusion with the remainder of the community or marital estate.  (However, the appreciated value of all such property during the time of marriage will generally be included as community or marital property and subject to division.)

With that said, it is still possible for your child's spouse to receive a portion of your intestate estate under certain, specific circumstances.

Child's Subsequent Death

Each state has a minimum time period that an heir must survive beyond the deceased's date of death in order to receive his or her share of the intestate estate.  This minimum time period is typically around five days. 

If an heir lives for the required minimum time period, that heir receives any share of the intestate estate that he or she is entitled to under the appropriate laws of intestacy.

This is true even when the heir dies prior to the actual distribution of the estate.  Although the minimum survival period is an average of five days, it takes much longer for any property from the intestate estate to be distributed to the heirs.

The share of an heir who dies after the minimum survival period, but before distribution of the estate, will simply be given to the deceased heir's estate.

Once it becomes part of the deceased heir's estate, the original intestate share will be controlled by that heir's will or, in the absence of a will, by an interpretation of the intestate laws applicable to that deceased heir. 

In the typical scenario, the daughter-in-law or son-in-law will receive all or most of the intestate share intended for a child who initially survives, but dies soon after the parent.  Every state's intestate laws classify the spouse as a primary heir who is entitled to at least a portion of the deceased spouse's intestate estate.  If the deceased child has a will, it is very common for most people to name the spouse as the sole heir, entitled to the entire estate.

Example

For instance, New Jersey requires each heir to survive the deceased by at least 120 hours in order to receive his or her share of the intestate estate (unless this requirement would cause the property to escheat).

Suppose a widowed New Jersey resident has a $500,000 intestate estate and two living children, Stanley and Oliver.  At the time of their mother's death, Stanley and Oliver are also New Jersey residents and are each married with two children.

According to New Jersey's intestate laws, each son receives an equal share of their mother's $500,000 intestate estate.

Although he is living at the time of his mother's death, Stan unexpectedly dies one month later and his mother's estate is distributed eleven months later.   Despite the fact that he is not living when the estate is distributed, the $250,000 share still belongs to Stanley because he survived his mother for a time period greater than the required 120 hours after the date of her death.

When the estate is distributed to the heirs, Stan's $250,000 will simply be paid to his estate.  Once it is part of Stan's estate the intestate share will be distributed according to New Jersey's intestate laws, but with reference to Stan.  It may also be important to note that Stan's death will not affect Oliver's share and he will still receive his $250,000 in full.

Of Stan's $250,000 share, the least his spouse will receive under New Jersey's intestate laws is $156,250 and she may receive the entire amount.  If she is the parent of both his children and does not have any children of her own by someone other than Stan, New Jersey law will grant the entire $250,000 share to her as the surviving spouse.

Of course, if Stanley is a resident of any other state, his intestate estate's apportionment will be controlled by that state's intestacy laws.  (If you're curious about how your state laws will divide your intestate estate, open the Intestacy Calculator™ for your state.)

Application

Many people would not be concerned with their estate property being given to a child's spouse in these circumstances.  Many other people would prefer to have their property given to the grandchildren, rather than the child's spouse.

Once it is received, the child's surviving spouse can use the child's the property however he or she wishes.  Although the property was received through the deceased spouse's family, the surviving spouse does not have any obligation to use that property for the benefit of the deceased spouse's children.

Alternatives

As one method to protect against this situation, a parent can very easily draft a will that 1) extends the length time required for survival, and 2) names the grandchildren as alternate beneficiaries.

Although this provides some protection, most wills extend the survival period to a time period of about one month.  If the intended beneficiary dies at any time after the one month period, it will result in the same outcome as above.

Another method that provides even greater protection is placing the property into a trust that names the child as a primary beneficiary while living, followed by the grandchildren at the time of the child's death.  The property can be placed into this trust while the parent is living or the parent can draft a will that creates a trust for this property.