Magnus will be the one to propose first.
I mean, just think about it. We've already established that Alec is the one who says everything on his mind, the devastatingly blunt lover. But let's not forget that he already asked Magnus to move in once, and was denied. He might want to get married, but he'd probably wait for Magnus to make a move, or talk it out first, just to be sure. Because - let's not forget - he's Alec Lightwood, Head of the New York Institute and one of the most powerful and influential Shadowhunters for centuries together, but he's also Alexander Gideon Lightwood, Magnus Bane's lover, hesitant and soft, but also strong and kind, and everything in between.
Which is exactly why I think Magnus will propose first.















