I recorded Once from the TV recently and can confirm that the dialogue in the opening scene is as we reported it earlier in this thread, so the junkie was certainly meant to be his brother.

Incidentally there was a report on Irish TV (RTE) News a couple of nights back about the music room in Waltons, the shop where Glen and Marketa go to practice in the movie. It said that playing "Falling Slowly" was banned in the shop because the staff were so fed up of hearing it.

I heard a similar story a few years back about a guitar shop (I think it was in London) where anyone trying out a guitar by playing the opening bars of Deep Purple's "Smoke on the Water" was thrown out on their ear.