A very good question - it was probably because they were horny and male and... Really those two things right there were enough beyond the attraction they felt to one another because... Really that attraction was very obvious right now. Very.
He really tried hard not to laugh at Brodie's expression. Really. Instead he smiled very broadly because it was kind of cute. He looked like a surprised mouse. (Which was a lot better than a surprised hamster.) Yeah, his words could be translated in a lot of ways but he only meant them in one. And apparently he was going to have to explain fully so he focused on gathering a little more blood to his brain so he could actually think of the words and form complete sentences.
Humming into that sweet kiss which was very different than the previous ones, his grin turned into a gentle smile, "Brodie... I kind of... already called you my boyfriend in conversation." So yes, he was very sure. Reaching up to cup the Aussie's cheeks with both hands, fingers curled just behind his ears, he shook his head a little, "I wouldn't bring it up if I weren't."