NFL Connections #64, Answers
The full solution: all four groups and the 16 names, sorted from the easiest group to the trickiest.
Patriots dynasty cornerstones
Tom Brady, Bill Belichick, Rob Gronkowski, Julian Edelman
1970s Steelers cornerstones
Terry Bradshaw, Joe Greene, Franco Harris, Jack Lambert
1980s 49ers cornerstones
Joe Montana, Jerry Rice, Ronnie Lott, Bill Walsh
1960s Packers cornerstones
Bart Starr, Vince Lombardi, Ray Nitschke, Paul Hornung