Half siblings definitely looks like a good possibility--the cousins look like cousins, the aunt looks like an aunt, and the suspected half sibling looks like a half sibling--all of those people came up in the range you'd expect to see.
Network President Jenny LeFevre, Agent Orange Victims and Widows Support Network, attributes more than 250,000 deaths to Agent Orange, a toxic herbicide the U.S. military sprayed over Vietnam from 1962 to 1971.
I do happen to have a letter that I got from the US Army in response to an inquiry I made of any knowledge that they may have regarding agent orange spray missions that occured in the area of Binh-thuy AB, or Can-Tho areas, during November 1968 to November 1969.