If a corporation sole wants to become a corporation aggregate, does it need to be dissolved first?

No. There is no point to dissolving the corporation sole of one member to enable the corporation aggregate to emerge from it. The Corporation Code provides no specific mechanism for amending the articles of incorporation of a corporation sole but Section 109 of the Corporation Code allows the application to religious corporations of the general provisions governing non-stock corporations. In non-stock corporations, the amendment needs the concurrence of at least two-thirds of its membership. If such approval mechanism is made to operate in a corporation sole, its one member in whom all the powers of the corporation technically belongs, needs to get the concurrence of two-thirds of its membership (Iglesia Evangelica Metodista v. Bishop Lazaro. GR. 184088 July 6, 2010).