The first two people created on Earth were Adam and Eve. You can follow their lineage in Genesis Chapter 5 to show that Noah was a descendant of Adam and Eve (Gen 5:29). Noah married and had three sons: Shem, Ham, and Japeth. Noah, his wife, his three sons, and their wives (each had one wife) were the only people on board the ark and the sole survivors of the global flood. After they got off the ark, God commanded them to be fruitful and multiply (Gen. 9:7). The three sons had many children with their wives (see Genesis Chapter 10 & 11) and we are all descendants from them (Gen. 9:19). Therefore, we are all descendants from Adam and Eve, and therefore we are all related.