Were you born after Noah was born? Then you are related to Noah.
It really is that simple.
But if you would like a more complex explanation, here it is: Around 2349 BC (according to James Ussher's dating system), a massive flood filled the entire earth. This flood, usually referred to as "Noah's Flood," destroyed everyone living on the earth— everyone, that is, except for eight people.
Scripture tells us the names of only four of the eight people who survived the flood: Noah, Shem, Ham, and Japheth. The other four people who survived were each of their wives.
Since the seven people who left the ark with Noah were all in some way related to Noah, it is simple enough to conclude that everyone who has lived after Noah's flood is also related to Noah. This fact is clearly supported by Scripture:
Now the sons of Noah who came out of the ark were Shem and Ham and Japheth; and Ham was the father of Canaan. These three were the sons of Noah, and from these the whole earth was populated. (Genesis 9:18-19)After all the corruption in the pre-flood world, after all the destruction, and after nearly a year on the ark, Noah and his three sons left the ark. From these four men and their wives, the entire earth was repopulated.
Now I know that there are some people who would object to such a statement. Such objectors might try to claim that there were other people on the Earth who were not destroyed by the flood— and that since those people were not related to Noah, it is impossible to conclude that everyone on Earth is related to Noah. This objection, however, has no basis in Scripture. In fact, such an objection is directly contradicted by Genesis 9:18-19, as well as everything else that Scripture has to say about the flood.
If there is one thing about the flood that Scripture makes clear over and over again it is this: Noah's Flood was a global flood. During the flood, the highest of the mountains were covered (Genesis 7:19-20). Every living thing with the breath of life died (Genesis 7:21-22). And only Noah's household survived (Genesis 7:23). How much clearer could it get?
Noah's Fall - Genesis 9:20-21 Bible Commentary
The Destruction of The City of Enoch - Genesis 7:17-18
What Is The Noahic Covenant? - Genesis 9:12-17
The Origin Of The Death Penalty - Genesis 9:5-7
The Cave Men of Genesis - Genesis 4