Depends on how you mean. "Bloodlines" is usually taken to mean "inherited traits," and there is likely some of that involved
However, preparation and training are far more important, and the kids of NFL players grow up immersed to some degree in the culture of the game, and have greater exposure to and opportunities to train with better coaches, trainers, and programs if they so choose, simply through the contacts their fathers develop in the NFL. That's the far greater impact of "bloodlines."
There's also a measure of confirmation bias at work, too: how many children of former NFL players fail to make it in college or the pros? You'll never see that story written...