CRA notes that two unrelated 50% shareholders potentially could both be related to the corporation based on Duha USA rights and s. 251(5)(b) rights

An “individual pension plan” as defined in Reg. 8300(1) of the Regulations includes a defined benefit registered pension plan having fewer than four members if at least one of them is related to a participating employer in the plan. Respecting where two unrelated individuals each held exactly 50% of the (voting common) shares of the employer, CRA noted that under Duha, “the determination of whether a person exercises de jure control … must also take into consideration whether any specific or unique limitation on a shareholder’s power to control the election of the board or the board’s power to manage the business and affairs of the company, is manifested in either the constating documents of the corporation, or any unanimous shareholder agreement” (USA), so that either individual could have de jure control and be related to the employer under s. 251(2)(b)(i).

Either individual could also be related by virtue of a s. 251(5)(b) right, as to which CRA noted that it was possible that both unrelated individuals could be related to the employer:

While paragraph 251(5)(b) does not deny that actual control is held by the person who has the direct ownership of shares, another person could have control simultaneously as a result of the application of one of the rules in paragraph 251(5)(b).

Neal Armstrong. Summary of 11 May 2017 Internal T.I. 2016-0665931I7 under Reg. 8300(1) - individual pension plan, s. 251(2)(b)(i) and s. 251(5)(b).