As in many countries, family names (surnames) come from one of several paths. Your surname might be the result of the family profession, for example, Thatcher, like the former prime minister of the UK, means that the person who took that surname worked making roofs from straw, also known as "thatch", or someone who has the last name of Cooper, his ancestor made barrels! Other family names trace their history back to other sources, like Thompson or Thomson, which means "the son of Tom, or Thomas". In some towns you many have many people with the same last name, so choosing the first name is important. There are many choices though for first names, hundreds to choose from! But, sometimes people want to carry on a tradition and give their children the names that have been part of their family for many years, such as Thomas Jones who might name his son Thomas as well. This can be confusing! But generally people in their circle of friends will know which Thomas Jones is being referred to. You might ask, "Do you mean Thomas Jones senior or junior?" (father or son) or the son may go by a "nickname" like Tom, or Tommy, or even young Tom!

that's the problem in all of the ocident, not only in US. Here in Brazil there's a lot of people called Jose, or Antonio. That's why we have a family name (sometimes 2 or 3). So, people have a first name (john, walter, willian) and it can be repeated, and a family name, which is more rare (like simpson, bauer, gartner, hanks). With that, it's rare to exist two people with exact same name, but it may happen.