Well so much for my belief that the parents usually have some idea! I guess that's not always the case. I suppose some parents are ignorant about it and some others just don't want to know. I'm glad you voiced some concerns, ican. Imo, that's all you could really have done.
I don't think ds would have listened if you had tried any harder or if anyone else had. Imo, he was just lashing out because he was upset and maybe embarrassed that he didn't listen to what you did tell him. I'm glad he's adjusting. I'm sorry it's taking dil longer, but I'm sure she'll adjust, too, in time.
Of course, you feel bad that gs has this condition. Idk, but I imagine that feeling of helplessness comes from the realization that you can do nothing to change it. And you can't. Neither can the parents. But now that they have a diagnosis, surely, they will get advice on how to handle gs. Since you often take care of him, I'm sure they'll share this information with you. Dil might not feel up to talking with you, right now, but ds can fill you in. Then, as you say, you can "pull together" with them - and, perhaps, not feel so "helpless."