A stunning new Tv documentary about Bing Crosby features revelations his twin boys, Dennis and Phillip, from his first marriage may have suffered from foetal alcohol syndrome.

While researching the expose, which aired in America on Tuesday (02Dec14), director Robert Trachtenberg came across footage of the boys, who died three years apart in the 1990s, and felt sure there was something visibly wrong with them.

He tells People magazine, "I took existing photos of the twins and showed it to a couple of specialists at Usc (University of Southern California). When they’re (babies) born (with foetal alcohol syndrome), it affects their skull and their nose, and it manifests itself physically as well. The specialists looked at them and said, 'Yeah, this is a like a textbook case of foetal alcohol syndrome'."

Trachtenberg looked for clues and evidence that suggested the White Christmas singer blamed his heavy-drinking wife Dixie Lee for his sons' condition, but came to the conclusion that the singer, who died in 1977, may have gone to his grave without knowing the truth.

He adds, "I couldn't find anything where he blamed her. That's the other tragedy of this whole situation. She (Lee) died at 41. Nobody really had any significant way to treat that. Kathryn, Bing's second wife, says in the film it was a terrible way to die.

"So, to add insult to injury, you have this situation (with the twins) on the one hand and then she dies on the other. We could have done a whole other film just about that."

Dennis Crosby killed himself in 1991 and his twin brother died of a heart attack in 1994, a year before sibling Gary's untimely death. Bing and Hall's other son, Lindsay committed suicide in 1989.

Trachtenberg's film also features new interviews with Crosby's "second family", including former Dallas star Mary Crosby.