Not on Trump's side here. But 1) Dean's brother Charlie wasn't in the military. Dean himself wrote in his 2003 book "Winning Back America" that "There was speculation that Charlie was in Laos because he was working for the CIA and I think my parents believed that to be the case."
2) Charlie Dean was definitely captured by Laotians. Dean went to Laos in 2002 & wrote that someone told him Charlie was killed by North Vietnamese but "I made the mistake of leading the witness...we don't know whether Charlie was killed by the North Vietnamese or someone else."
3) Charlie Dean was buried in a bomb crater. The US dropped more bombs on Laos than Germany & Japan combined during WW II. This makes Laos, which is smaller than Michigan, the most heavily-bombed country in history.