The book of Obadiah is a message given to the Edomites. The Edomites are the descendants of Esau. Esau was Jacobs older brother that traded his inheritance for a bowl of soup.
The book is only one chapter long so it is a quick read and the cliff notes version of the book would look like this.
Edom, you did not help your relative Israel. You watched them suffer at the hands of their enemies and get taken to a far away land. In fact you plundered their land and gloated at their destruction. So now Edom will be destroyed by Israel’s return.
Obadiah ends this book with a description of Israel coming back to their land and all of Edom being destroyed by Israel. Verse 18 says “There will be no survivors in Edom. I, the Lord, have spoken.” So…. I don’t likely have a family tree that will go back to Esau.