I kind of feel the same way. While there are hints of it in The Molt Down, and A Rochhoof and a Hard Place, it really comes across as that to me in Father Knows Beast. The way Smolder kind of says that Spike doesn’t really act like a dragon, but then stands up and defends him against Sludge, just screams that she feels protective of him like a sibling or something.
I like to think this too. It would be pleasant to watch a deep and loving but non-romantic relationship develop between these two.
it was never said but in my head canon approves it
He is.