I was out doing the main quest with the husky bran while I was in black reach at one point he just disappeared he might of ran away. Ever since then I couldn't find him so I went back to fort dawnguard and bran wasn't there, only sceolong. When I asked sceolong if he wants to be my dog the option I already have a dog wasn't available so bran appears to not be one of my followers. What should I do? Is it possible for them to die?

Unless you're playing with a mod that makes dogs essential, yes Bran is probably dead.

Here goes the console command to move things to you:

Bran′s Ref-ID is XX01AA7B , where XX can vary between 00-03 and refers to which expansion (base game, dragonborn, hearthfire, dawnguard) that thing belongs to. It can vary from one pc to the other, but once you find out each one of them, everything in each "expansion" has that same reference. For instance, in my disk Dawnguard is "03", so Bran′s reference is 0301AA7B. As an example, just to be clear, it would look like this:

You can find these reference IDs for any Named character in the wiki.