In the netherlands Surnames only became forced by law in 1811 (or 1812). Before that many people where know by their patronyms (father sname), e.g. Pete, son of John was called Pete Johns; when Pete got a son himself he would be called e.g. Jim Petes.
So in 1811/12 people were forced to come up with a surname. Some were quite creative, and called themselves with some funny names, comparable to Doodle or whatsoever, many on the other hand were
less creative, and just registered their patronym', or the place or state they came from. So in the netherlands we have many people called 'Jansen' (='Johns son') or 'de Vries'(=the Frisian) who are not related. the only thing they have in commen is either the first name of one of their ancestors (jan (or john), the most common surname in Holland), or the place they came from (e.g. Frisia: the northernmost part of the Netherlands).
Now, in some situations people did have a surname well before 1811. This was the case for instance for quite well of families or nobility, or families who thought quite highly of their ancestors. Undoubtedly they will have many descendants with the same surname, all related, however back in 1811/12 some people, when chosing their names, picked one of these names, even though they were not related...
So, having the same surname is not often a guarantee of being related, especially if you have a name which is quite common in some place.
Finaly, there is another thing you have to keep in mind, and that is how you define "I am related to..."
Some people say that, actually, we are all related to eachother. This is not only because there's Adam and Eve (remember?), but also scientific people (genticists) think we all have a common ancestor from somewhere in Africa. So bothe sides of those camps say that
we're all related (means looking at a surname makes no sense).
Other people, or in other situations you look at "being related to someone" in a different fashion, i.e. being a close relative or a distant relative. Looking at the paragraph above this one you and I are related,
however whether you would call that related as in a day to day sense, I doubt.....
Cheers, LD