The story behind people thinking they were brothers was because it said it in an early version of the movie script. It was taken out of the script, therefore, people made their own headcannon on them being brothers or not.
Oh my god. I loved that quote too. During that scene, when I was watching it with my mom, I felt awkward because of all the gayness going on even though there was nothing going on damned Davies just WANTS us to ship it. XD