It's tough to find information about shareholders but according to his wife the former publisher of the Green Bay Press-Gazette and president of the Packers Hall of Fame board Michael Gage was the largest one when he died five years ago.
It might be possible there are some people having a significant amount of shares though as the articles of incorporation prohibit any person from owning more than 200,000 shares to protect against someone taking control of the team.
It appears Mr. Gage and one other individual held 200,000 shares at the time of the 2011 stock issuance.
Here are some factoids on share ownership and how those two individuals would have come by those substantial holdings:
According to this Wikipedia page [
https://en.wikipedia.org/wiki/Green_Bay_Packers,_Inc.], prior to the '97-'98 share issuance there were 1,940 share holders holding about 5,000 shares. The page inconsistently states there were 1,940 shares outstanding at the time, one per shareholder. If the other data is correct, it looks like there were 300 shares coming out of the 1950 insolvency/reorganization with another 4,700 issued in 1950 bringing the total to 5,000 shares up to the '97-'98 share issuance.
In conjunction with the '97 - '98 share issuance, the incumbent 5,000 shares were split 1,000-to-1. So anybody holding one share prior to '97 - '98 now held 1,000 shares, and the incumbent 5,000 shares became 5,000,000. At the same time, the max shares one could own was bumped from 200 to 200,000 in line with that split.
The '97 - '98 new share issuance added 120,000 new shares and the 2011 new share issuance added another 269,000 shares. That would bring the total shares to about 5.4 million. That number is a little off, but close enough llustrate a couple of points.
This link [
https://blogs.wsj.com/totalreturn/2012/01/13/are-the-green-bay-packers-the-worst-stock-in-america/] says the two largest shareholders at the time of the 2011 share issuance held the max 200,000 shares each.
One of those shareholders was evidently Mr. Gage. Since he was the third generation publisher of the Press Gazette, it would stand to reason those shares were passed down from his grandfather or father who owned 200 shares pre-split dating from purchases in 1950 or prior.
I'm not finding anything on the disposition of Mr. Gage's shares upon his death, whether Mrs. Gage retained them through bequest or whether she disposed of them, perhaps by donation to the Packer Foundation. She's not on the Board Directors, if she was so inclined, as would be appropriate for about 4% voting interest. I couldn't say if she's still alive or if those shares passed on to somebody else.
Anyway, if Mrs. Gage still holds those shares and one could find out who the other 200,000 shareholder happens to be, those two individuals would be together holding about an 8% ownership which is significant voting power. If one were of an activist bent, lobbying those individuals would be the place to start.