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.
1 Exposure to Agent Orange in Vietnam. Exposure on land in Vietnam or on a ship operating on the inland waterways of Vietnam between January 9, 1962 and May 7, 1975.  C-123 Airplanes and Agent Orange Residue. Possible exposure of crew members to herbicide residue in C-123 planes flown after the Vietnam War.