Where Mr. A and Mr. B, who each own 50% of the shares of A Ltd. and B Ltd., enter into a shareholders' agreement with respect to their shareholdings in both corporations which include clauses that fall under s. 251(5)(b) (for example, the obligation to buy and sell if one withdraws from the business), the two corporations will be related for purposes of the exemption in s. 55(3)(a), unless s. 55(4) applies.