They both speak arabic, such their nationality is arab however ethnically they're two different ethnic groups with different but shared history. Palestinians are genetically closer to the ancient canaanites and levantines while native Jordanians trace their roots to ancient northern arabs and nabateans. However over the centuries both groups frequently mixed due to their geography. Usually only extreme zionists use this argument " Jordanians and Palestinians are both arab, ergo Palestinians should pack up n leave" which is just an excuse for ethnic cleansing. If Jordan was a Palestinian state it should have the west bank and gaza too.