Is everyone related to each other?

Biblically Speaking

Yes. According to The Bible, God created a man named Adam and a woman named Eve and told them to populate the earth. Therefore, from a biblical perspective, our ancestors came from Adam and Eve, so we are all related.

Non-Creationist View

Yes. Studies of mitochindrial DNA indicate that all current humans had a single "mother", or common ancestor, whose DNA pattern has been replicated in all Homo sapiens on Earth.

In fact according to evolution, not only are all humans related to each other through a single common ancestor (that lived ca. 2.5 million years age, with modern humans having a common ancestor only a couple 100,000 years ago if not sooner), but every living thing is related to every living thing through a single common ancestor (that lived ca. 3.4 billion years ago).