Are Jeju island people ethnically and genetically Korean?

Iam Korean and me and my family is from Jeju and i wondering if we ethnically Korean (the answear is probably yes but i just want to make sure) i know we the people of Jeju have there own distinct dialiet and some cultural differences between mainland Koreans but i have never seen a differnce between us and mainlanders in terms of looks and features, i was just wondering becasue the internet wesite says other wise but i dont believe us to be differnt from mainlanders in terms of looks and feuters, and if the answear is no then we are still Korean and will always identify us as being Korean.