Thank you for the responses. I will try Kids Konnected, also -- as a hospice nurse, I thought to myself before I even entered my Google search, "They're probably going to be mainly for cancer." But maybe even some of the cancer groups are open to kids of parents with other life-altering illnesses. Won't hurt to try...
I also found "griefnet.org" which has support groups for kids and teens "facing any major loss." I e-mailed the founder of the group to find out if the groups focus on kids/teens who have experienced the death of a loved one, or whether it has a broader focus on grief in general and coping with change and loss. She said it's open to kids facing any kind of loss, and that the kids tend not to post a lot but are kind and supportive when others do. I have a feeling that most of the kids have probably lost a parent or loved one, but have not yet actually taken the step of joining so that I can check it out further. An option, anyway.