How annoying for you JM! I know we're only supposed to weigh ourselves once a week, but I'm addicted to weighing myself at least once (and usually more) every day even though, like yours, my scales are regularly 3 or 4 lbs. different than the ones at Weight Watchers - I just feel a need to see the number, even though I can fluctuate a few pounds in the same day! I think it's a psychological thing to keep me on track and away from mindless snacking.
Anyway, I guess I should be saying that you should forget about your scales and your brother's scales and just rely totally on the once a week weigh-in at Weight Watchers, using reliable scales - but I don't even follow my own advice