missroserose | Is there such a thing as the reverse of a fair-weather friend?

I've had a rough relationship with my brother. Plenty of it is my own damn fault - I remember my mother warning me when I was younger that I should treat him better, but when you get into the habit of talking over somebody and basically acting like they aren't their own person because they're too in awe of you to stand up for themselves, it's tough to change (especially when you're young and aren't even sure what a healthy sibling relationship looks like). A lot of it also comes from plain ol' personality dynamics - when you're a shy and quiet kid, and your father isn't much of a role model to you (and eventually leaves), and your mother and older sister are incredibly opinionated and outgoing and charismatic, it's easy to feel lost in the shuffle. My mother and I joke sometimes that the reason he became a firebreather is because it was the only way he felt like he could get anyone to pay attention to him. Maybe it's not that much of a joke.

We took fairly different paths away from our home. I took the more traditional route, going to college (some) and getting a job, getting married, gradually getting stable with some help from my mother (and, once Brian and I were together, future-mother-in-law). Ace, on the other hand, took the school-of-hard-knocks route - left home at 18 more or less penniless, flew across the country and never looked back so far as I know.

We've been in contact sporadically over the years, but there have been long stretches where I haven't heard from him. Usually these occur when things aren't going so well for him, and usually-usually they'll be precipitated by my trying to give him advice and his spouting off about how I'm on my high horse and how dare I tell him how to live his life. (I suppose it's worth pointing out that that's not the tone I'm meaning to take at all, but part of the problem is likely that we mostly communicate over IM, where it's easy to misread tone - especially when your own mental state is overwhelmingly negative.) So then he disappears for anywhere from a couple of weeks to a couple of years, until things get better for him and he can talk to me again.

I suppose it's pretty obvious that this has happened again, and frankly, I'm just not sure what to do with this. I do care about him (obviously), and I don't want to shut him out of my life like I have my father, but if this were a friendship I'd frankly advise the person involved to move on - their "friend" just doesn't have the social maturity to be somebody worth knowing. But since it's my brother, and a lot of our problems are my fault, do I have a responsibility to keep going back and trying to repair things? How many times do I put up with being hurt like this? At what point does that responsibility end?