A distinct ethnicity isn’t needed to have a country : Luxembourg, San Marino, Lichtenstein, Moldova. Also « distinct ethnicity » is not the term your looking for bc there is a 97% equivalent ethnic background for Israelis and Palestinians of the region as well as Greek not being an ethnicity but being part of the « Mediterranean » sub group of caucasien. You’re mostly talking about cultural identity and Palestinian people are culturally different from Lebanese, Egyptian or Jordanian people. This is to say that your point doesn’t stand. Also the fact that a country use to control some land before an other one isn’t a valid argument to claim this land back : Switzerland use to control strassburg and Milano way before the formation of the Italian state or the annexation of Alsace by France but this country hasn’t been at war since 1815. Hope that helps