I've been watching this thread for a few days and it's been driving nuts because I haven't had the time to reply until now.
Don't make the mistake of thinking that Emmett and Rosalie don't truly love each other because they are only interested in the physical aspects of the relationship. They DO love each other and they love each other deeply. They simply choose to express it differently than the others.
In the "Emmett and the Bear" outtake, Emmett reverantly describes his first reaction to seeing Rosalie. Bella mentions her growing relationship with Emmett and says, "It had to do with how we had both been chosen to join the family; we’d both been loved – and loved in return – while we were human, though very briefly for him." That statement shows that Emmett and Rose fell in love instantly.
In Eclipse, Rosalie tells Bella, "I got luckier than I deserved. Emmett is everything I would have asked for if I’d known myself well enough to know what to ask for. He’s exactly the kind of person someone like me needs. And, oddly enough, he needs me, too. That part worked out better than I could have hoped.”
Stephenie addresses their relationship several times in the Personal Correspondances. In a question about their weddings she says, "Rosalie is all about show; Emmett loves to make her happy–hence, lots of elaborate weddings." When you truly love someone their happiness is one of the most important things to you.
In a question about the different relationships between the Cullen couples, Stephenie stated, "Rosalie and Emmett’s might be seen as the most superficial in a way, because their relationship is so intensely physical. But they are entirely committed to each other, so that’s hardly superficial." In a follow-up question about the different relationships she further explained, "I want to say that the traits I assigned to the Cullen couples were not to be understood as totally definitive; these characteristics, spiritual, physical and mythical, were merely the most prominent facet of each relationship—other facets are still quite strong with each."
They ground each other, preventing each from floating away in their extremes. Rosalie's pessimism keeps Emmett from rushing off without thinking a situation through. Emmett's jovial nature and adoration keep Rosalie from drowning in her angst.
They love each other as truly and deeply as any of the other couples. They just choose to express that love physically and passionately.
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