Lots of gullible people purchase various trinkets that display the "family coat of arms" without realizing there is no such thing. Coats of arms? Yes. But "family?" No. There is no such thing as a family coat of arms.
NOTE: I do have to point out two exceptions. Several hundred years ago, merchants in Belgium did adopt coats of arms that were similar to the coats of arms displayed by nobility, but with some differences. Those Belgian coats of arms, or family crests, displayed by merchants are assigned to families and are inherited. However, coats of arms displayed by nobility in Belgium are not inherited.The truth is, except for the exceptions listed, families do not have family crests, correctly known as "coats of arms." The crest is only a small section of the entire design and was usually depicted above the helmet.
In addition, Samurai soldiers in Japan also have family "insignia" that are assigned to families and are passed down from generation to generation. The Japanese symbols do not look like European coats of arms with shields and helmets, adorned with lions and dragons and birds and such things, however.
If your male line descends from a few families in Belgium or from the Samurai class in Japan, you can ignore the rest of this article. However, if your family comes from the British Isles or any place in Europe, other than a few families in Belgium, this applies to you.
Coats of arms were designed for use in battle. If you can imagine wearing a full suit of armor, complete with a helmet with tiny eye slits for vision, the combatants had a difficult time differentiating friend from foe. It was bad form to stick a broadsword into your friend's midsection, although that did happen occasionally in the heat of battle. As a visual aid, the knights and a few other combatants started wearing brightly painted designs on their shields and elsewhere, designs that were known to their fellow combatants. The intent was to help their fellow combatants distinguish friends from foe. The brightly colored insignia was used on shields, on clothing, and on horse dressings.
Occasionally, a knight might have an attendant or two, such as a groomsman who tended the horse or even multiple horses. The attendant also might be a “squire;” a young apprentice who hoped to become a knight on his 21st birthday. The attendant might wear clothing with the same colors as his master, signifying that he was a part of "the team." However, such attendants normally did not wear armor.
If the knight had a close relative in battle as a combatant, such as his son, a brother, a nephew, or other relative, that relative never wore the same insignia as the first knight. In battle, sons never wore the same insignia as their fathers. Each had his own insignia and colors.
Off the battlefield, coats of arms were also used during tournaments to distinguish competitors. Knights, royalty, and a few wealthy individuals displayed their colorful crests and coats of arms as a symbol of themselves. In effect, the coat of arms said, "This is me." Coats of arms were never used to declare, "This is my family."
In fact, the only time that the same coat of arms can be used by more than one person is when the eldest is dead. At that point, the direct heir (typically his oldest son) can petition for the right to bear the same arms that were used by the deceased.
In the case of multiple sons, or when the father was still alive, all the sons could use SIMILAR coats of arms as their father but always added their own variations to the design. Each son created his own variations. These variations are called "cadency" and the son's insignia is referred to as "cadet coat of arms." When the father died, the oldest son removed his personal cadency, reverting the coat of arms back to his father's original design. The other sons kept their cadet coat of arms; they never used the father's original design.
Daughters can also inherit the coat of arms if no sons are living.
In olden times and today, not every coat of arms can be used by everyone with that surname. First of all, not everyone with the same surname is related. I suspect there was more than one knight named Smith, and they certainly didn't want to wear the same coats of arms in battle!
Despite what the man at the pushcart told you at the local shopping mall, the rules always required that a coat of arms was for use by a single living individual, not a family. A coat of arms is similar to an individual's signature and was used as seals on official documents.
Another requirement has been in effect since the 15th century and still applies today: the person who wishes to display a coat of arms must first register the design in a central clearinghouse and obtain permission to display it. Registration was required in the 15th century, and it is still expected today. If you are displaying a coat of arms without written permission, you are guilty of an impolite form of forgery. In the U.S., you won't get arrested for doing so because the U.S. has no laws concerning display of forged coats of arms. Such laws do exist on the books in England and in many other countries, but they are rarely enforced.
The official office regulating coats of arms and the granting of new arms for England, Wales, and Northern Ireland is the College of Arms (http://www.college-of-arms.gov.uk/). It was founded by King Richard III in 1484. If you would like to display your own personally designed coat of arms, and if your male ancestry is from England, you start at the College of Arms. That would be true even if you now live in the United States. You cannot apply online but you can do so by mail.
To learn more about coat of arms granted in Scotland, visit the Court of the Lord Lyon (http://www.lyon-court.com/lordlyon/CCC_FirstPage.jsp). Scottish descendants would apply to the Court of the Lord Lyon.
Canada has its own heraldic office, the Canadian Heraldic Authority (http://www.gg.ca/document.aspx?id=81). The rules for applying for a coat of arms are slightly different in Canada. Contact the Canadian Heraldic Authority for details.