You’re not doing anything wrong, but you should think about just not doing anything at all.
The death of a parent is terrible, and such family tragedies can wreak havoc on relationships. He’s grieving, and there’s just no play book for grief. Everybody does it their own way, for as long as they need to. The best thing you can do is fall back a little. Let him know you are there for him in whatever capacity he needs — and that might include him taking time to bunker down with his brothers. Allow him his space. It hurts to watch someone you care about suffer, but it’s the only thing you can do.
If you want to help him, he has to come to you.
When my dad died, I was a total wreck. I remember my girlfriend at the time desperately trying to reach out to me. In retrospect, I realize she meant well. It’s natural to want to put back together someone who is tearing themselves apart. But at the time, her pleas, tears, hugs, and sweet words just crowded a brain too full of whiskey, regrets, and darkness. I couldn’t deal with my pain and her agony at watching me cope.
Ultimately, it was one of the main contributing factors to our eventual, and messy, break-up. To this day, I mourn the fact that I had no perspective beyond my own emptiness at that time, and that I couldn’t recognize her good intentions.
You can’t be there for him now, not in the way that feels right to you. You can be there for him in spirit.. And you can be there for him when emerges from his fog.
Until then, I think it’s appropriate that he finds solace and support in his brothers.