He's certainly not the first former player to suggest this; but it is notable that not only did Brett Favre make this comment; but he did a video to accompany his message.
The three time league MVP said "Having kids play before high school is just not worth the risk."
Favre said he would support his grandchildren if they choose to play tackle earlier; but he doesn't plan to encourage them to.
"If they choose to play, I will support them, but I'm not going to encourage them in any way to play. That surprises a lot of people, but I'm just fearful of what concussions can do," Favre offered. "And it only takes one. Maybe I have had a thousand... It's just too risky. I'm not going to encourage them to play until there's a treatment."
See the PSA the Concussion Legacy Foundation produced below: