The main reason this wouldn't work is that the pair of them are already at the point where they love each other. Each of them knows that they love the other one and is pretty sure that it's mutual.

The thing that's stopping them from getting into a relationship is fear due to them both having massive (canon) abandonment issues.

One of my friends who is familiar with the canon suggested that Klavier in particular, but possibly Apollo as well, needs to get into therapy. They both need to overcome their pasts and gain the ability to even consider that they're worthy of love.

I'm not sure how to write therapy I've never needed or had. Might have to skip over several months.