So I am in a band consisting of 5 people: 2 guitarists, the drummer, the bassist and a vocalist (might be worth mentioning that the guitarists are brothers that only tend to see each other at practice). Due to the style of music we play we pretty much need everyone there to practice.
We meet up twice a week up to practice or write new songs and play gigs roughly once every two weeks.
We decided together that we would practice on Thursday evenings at 6:00PM after work and on Sundays because all of us were free at that time. This was working out fine until recently. One of the guitarists (I'll call him X) keeps showing up late to practices by 2 or 3 hours, or not turning up at all. X also makes it to every gig but barely and has caused us to not be able to have a sound check.
Each time he's late/doesn't show up he sends us a message stating that something has come up. This has been happening consistently for the last 3 months.
Now we don't want to kick X out of the band as he's clearly talented and brings a lot to the band when he's here.
My question is, what would be the best way to express that this kind of behavior can't continue without it negatively affecting the band/music?
Edit: We've spoken to X a few times about the issue and he usually just apologizes and insists that it won't keep happening. It seems as though he wants to stay in the band as he keeps pushing us to get more live shows.