I agree with Leopold. If his excuse was to go visit his ailing grandmother that'd be one thing, but to leave early to go play cards and get drunk sounds like an alcoholic to me.
I'd flat out tell him - you need to make a choice - either commit to us full time, or we'd rather not have you play at all. It's that simple.
I know exactly what you're going through. I played with a couple of brothers briefly. We played Star Wars (west end games version). They were roommates, and their sister, and one of their girlfriends played with us as well. Well, they insisted on playing on Thursday nights, since one of the brothers wanted to go clubbing on Friday nights, and sometimes on Thursday nights he'd either be really late, or would leave early to go to the club. And the other brother was always wanting to go to bed early since he would have something important going on at work the next day, or something. And the girlfriend was just there because the boyfriend wanted here - she wasn't into it.
So, eventually I left that group. Which was a shame, because they were decent people I could have easily hung out with, but the level of commitment just wasn't there for them.