The short answer
There is no single national rule. Each state sets its own limits. Some states say a notary may not act for a spouse, parent or child. Others do not list relatives at all and only forbid acting when the notary has a direct interest in the document.
Because a notary commission belongs to the person, any mistake or challenge lands on the notary, not on the relative who asked.
Why relationships create risk
A notary must confirm identity and willingness. With a close relative, it is tempting to skip the ID check because you know them. That shortcut is exactly what makes a notarization easy to challenge later.
Family documents also often involve inheritance, property transfers and care decisions, which are the same kinds of documents that turn into disputes.
There is also a trust problem. If a relative later disputes the paper, the notary becomes a witness in a family conflict, with all the strain that brings. Keeping family out of your notary work keeps those two parts of life separate.
Reading your own state's rules
Start with the notary handbook or statute from the office that commissions notaries in your state. Look for the words interested party, beneficial interest, or relative. If the language is vague, treat it as a reason to be careful, not a green light.
If you work for a company, check whether your employer has a policy on notarizing for employees' families.
A realistic scenario
Suppose your brother asks you to notarize a car title transfer to a neighbor. You gain nothing, and the neighbor is a stranger to you. In some states that may be allowed. Now suppose the title is being transferred to you. You are a party, and you must decline.
The first example still carries risk if the family tie later becomes an issue, so many notaries refuse both.
Practical alternatives
Ask a notary at a bank, a shipping store, a law office or a library. Many mobile notaries will travel to a home. For someone who cannot leave the house, a remote online notarization can work if the state allows it for that document.
If you are the notary only because no one else is available, wait a day and book an outside notary.
Fees are another reason to be careful. Charging a relative a full fee feels awkward, and doing the work free can blur whether the act was treated as a formal service at all. A neutral notary avoids that question completely.
If you already did it
If you notarized for a relative and later learned it was not allowed, tell the signer early. They may need to redo the notarization with a different notary. Do not alter the journal or the certificate. Contact the commissioning office if you are unsure how to correct it.
Common questions
Is it illegal for me to notarize my mother's signature?
In some states it is restricted, in others it is allowed if you gain nothing. Look up your state's rules, and when in doubt, use another notary.
Does it matter if I am a beneficiary?
Yes. If you benefit from the document, most notary rules treat you as having an interest, and you should not notarize it.
This guide is general information, not legal advice. Fees and procedures change; check with the office involved or an attorney for your situation.