There’s an entire section of Hamas’ Wikipedia page dedicated to it. The gist is that there’s testamony that Israel explicitly funded Hamas in order to counter the PLO. This was to ensure a Palestinian state would never materialize.
I have not researched the matter due as enough to have a full opinion, though I’ve heard multiple individuals state that it is almost indisputable that it happened.
Ethnicity is not what was being talked about just now; You were talking about DNA lineage.
Ethnicity deals with cultural self-identity, which includes religion and does not deal at all with DNA relation.
My understanding, though, is that Jewish culture actually has a long history of genealogy via family tree mapping long before DNA testing was available. That does have some ethnic connection as a cultural tradition.