That’s an easy one 😉
Jacob in Brothers Lost is eighteen years old, only a few months from turning nineteen. In both Brothers Found and Brothers Adopted, he’s seventeen, putting him shorter than Sam and Dean both. So, give him a little time, and Sam and Dean will both be looking up to him! (And Dean will be complaining all the way)
He just needs a little more time to get to his full height.
Brothers Apart 