For decades, the story of Boston mobster James "Whitey" Bulger's rise to power has paralleled that of South Boston's other famous son, his brother William Bulger, the former longtime president of the state Senate and former president of the University of Massachusetts.

The relationship of the two brothers and their separate relationships to the FBI have long been the focus of speculation and of past and current testimony.

WBUR's David Boeri has covered both brothers closely for decades, and he joined WBUR's Morning Edition to preview his profile of William Bulger, the next chapter in his special report on "Whitey" Bulger.