Yes, definitely. We are all descendants from a relatively small group of people, who were also all related, and who probably lived in Africa a bit more than 2 million years ago. By that time span, you can see that we are only very distantly related of course!
Yes, humans are all related to each other. You don’t even have to go back that far to see this. If you trace back your grand-parents to your great-grandparents to your great-great grandparents etc., then by the time you get the the Middle Ages, most people in europe share the same ancestors. So most europeans are not-so-distant cousins!