Yes, I believe its true that all of us are related. This is because we have the same father and mother- Adam and Eve. Our great ancestors must have been born to the couple. This definitely makes us all related.
All of the children of Adam and Eve, settled at different places around the world. Normally places that fulfilled their food and work requirement were chosen. Now the weather and other conditions of that place affected the color and skin and features of these individuals. As their population multiplied, they grew in number and spread around the world. And became distinct groups of people which later became individual societies and countries.
Thus, in essence we are all children of the same parents. Our differences in skin, religion, color are just to distinguish us from each other.