I was very close to my BIL - until he married the neighbor.
However, i still see him. I'm super close to the kids - and go to their events. We inevitably run into him at my sister's house if he is picking someone up or dropping someone off. My goal was always to support the kids 100% - so if he needs something FOR them, he knows that he can call me. He is also supportive of them visiting me (will drop them at my house, etc.). When he has said something stupid about my sister, I've reminded him that I'm also 100% on her team - so he has held his tongue on that stuff.

They married when I was a 20-something..and now that I am married with my own children, it is sometimes bittersweet...Like, he doesn't really know my husband and has only seen my kids a handful of times. I don't like him, but 20 year old me, who loved him and considered him a close friend sometimes is sad that I don't want him to be close to us.
usually, he does something genuinely F-d up about once every six months..and then I remember that he's a jackass.

Part of the answer here depends on the cause of the divorce and what the personalities of the players are like. I assume you'll be doing arranging exclusively through your sister (though I suppose you could see ex-BIL at a pickup or drop off if he didn't mind his kids spending time with you during "his time"), but may see your ex-BIL at some family events (birthdays, etc) if they have a cordial post-divorce relationship; if they don't, you will never deal with or see him again.

My sister is divorcing her husband. We spend a ton of time with them for holidays, vacations, weekend visits. The cousins are extremely close. I'm interested in hearing how this usually plays out for extended families. Will I see my BIL again? Since he is father of their young children - will I be arranging visits with him for the kids to get together - or does it all usually go through my sister when she has the kids?

I am heartbroken. I like my BIL, and I will miss him tremendously. Any experience or words of wisdom?