It doesn't matter how many shareholders there are, since an S-corp is not a disregarded entity, like a single-member LLC.
From https://en.wikipedia.org/wiki/S_corporation#FICA:
> As is the case for any other corporation, the FICA tax is imposed only with respect to employee wages and not on distributive shares of shareholders. Although FICA tax is not owed on distributive shares, the IRS and equivalent state revenue agencies may recategorize distributions paid to shareholder-employees as wages if shareholder-employees are not paid a reasonable wage for the services they perform in their positions within the company.
If you have data to support the contrary, please post your sources.