I don't think moving the tube of toothpaste to the medicine cabinet (if that's where it's normally kept--when I was a kid, the counter was where the toothpaste lived) is overstepping. I think moving items a small amount, as long as they are kept near the same location, is okay. My MIL tidied our counters the other day. There were a bunch of papers scattered about, and she put them in a neat pile without looking at them. That might be a little more "risky" since papers could contain information, but in general, I'd think that level of tidying up would be okay. Like if he'd left a newspaper scattered across the coffee table, stacking it up neatly would be fine (but I wouldn't throw it away). Wiping the counters, cleaning the bathrooms, wiping down the fridge and throwing away any old yucky stuff (or turning the fridge on if it were cleaned out and turned off), getting a few groceries, they're all nice ways to welcome your brother back. You could even treat him to a DVD of a movie that came out while he was gone that you know he'd like, or a book, or whatever.