[MatthewS]

I really think it boils down to animosity, and to be fair, I think Callum has it worse then Dexter.

I think Dexter is pretty content with the relationship he has with Charlie, and understands and is respectful enough of the relationship Charlie has with Callum. On the flip side, I think it genuinely gets to Callum that Dexter and Charlie are close, and he goes out of his way to talk bad about Dexter when the opportunity arises, specifically mentioning how Charlie shouldn't trust Dexter and he isn't who he says he is, etc.. But when I see Dexter talk about Callum to Charlie, he always mentions his own personal feelings about Callum, in a way that doesn't necessarily try to influence how Charlie should feel about him. Decent way to go about it imo. Can't say I feel the same about how Callum approaches it.