Michelle,
I'm sorry it took so long to sort out a response to this one. I have very mixed feelings about this. While I worry about forced visitation in situations where one (or more) sibling is abusive to the other(s), I think the kids should have some assurance of the permanacy of their sibling relationships, even if they are not living together.
As always, this is colored by my experience. My oldest boy has two bio brothers that we know of. Each child was removed from birthmom at birth. We have some contact with the youngest brother, but the adoptive family of the oldest brother has not been open to any contact because . . . "they don't know each other anyway" and "he doesn't need more siblings". They have our contact information, hopefully they will get in touch if they reconsider this.
A friend has a son with siblings still in foster care. Last year they were moved to a new placement and she was not notified until she called to talk to them a week later.
It would be great if the adults involved would voluntarily protect the sibling relationship in cases where it is safe to do so. Unfortunately, that doesn't always happen. I'm not sure there is one perfect solution to this. I would hope that needing a court order to maintain contact would be the exception. Anyway, that's my two cents.
Julie

I hear you Julie, It just isn't a cut and dried answer ever. It just HAS to be a situation by situation decision and the parents have to be making good decisions -...You just have to respect a mom who doesn't want contact - for whatever reason, It is HER family now.... I wouldn't want the court mandating visits for me.. But I hope I'd also do what is right for the children..

I appreciate you taking time to give such a thoughtful response. Thanks Michelle