[Delumine]

This is a terrible idea, and already bearing fruits of disrespect. Once they get married, they're going to answer to each other, and treat you as a "3rd" wheel. A lot of times (not even trying to be sexist), the opposite gender have power over us through love and intimacy that can blind us from logic; this can affect family, friendships, and sense of self in being an autonomous person.

Worst case scenario, you piss off the incumbent employees (which could cause them to go elsewhere, where their contributions are respected, and further down the line you wield no power as it's 2 of them vs you.

You need to be steadfast in your resolve, and have a private conversation with your friend and cofounder talking about these things. Stressing that although love is a beautiful thing, it's not always permanent and to focus on yourself, and what you've built first. It does sound like she has been contributing, but adding her as a co-founder with equity like that, is just his pants speaking.

Draw boundaries, and stand tall. Propose the following, if he wants her to have equity.. maybe he can sequester some of his to her? After all, they're gonna be married soon right :^)?