Yeah—I mean, I think you can read slash into those relationships if you really want to, but they're not at all on the same level of real significance as Ewen/Keith. That's an insightful comment about the 'brother' language! Something I find fascinating about Ewen/Keith from Ewen's point of view is how Ewen is surrounded by people who love him, happily, in various ways that are totally acceptable and fit into the society he lives in—and then Keith comes along and introduces something completely different into his life, and it's incredibly significant to him.