Yes, there will be plenty of people who could spill the beans including the siblings themselves. My point is that the less people who know, the less chance of exposure before they're ready. We also don't know the new living situation - are there other vulnerable people living there who need protection and definitely don't need whatever media circus would descend on the residence. I imagine no one wants the parents or extended family to know.
I'm not disagreeing that it would neat for them to have the continuity of normal human connections and emotional support they've received! But, I have to assume and accept that the siblings were counseled about this and hopefully understand that while it's necessary for now, it won't be forever. Since they are adults - albeit vulnerable at this point - they are legally able to contact whomever they wish? It's possible that at least one caregiver had already given one of the siblings their contact info.
Human nature. Someone may have done it early on without anticipating it would be forbidden later "Hey, if you ever want to just talk or have any questions, give me a call." or "If you want to know more about XYZ, give me a call - it'll be fun to cook, bake, paint, ride horses, do laundry (whatever) together!" To me, something like that seems perfectly understandable. Most people enjoy being able to help others. I could easily see myself offering my number "if you ever feel like wanting to make a collage, decoupage, sew, cook or bake something". I dunno. :dunno: It's easy to criticize when we don't know all that's going on and what their therapy entails.
I also don't understand the completeness of a break, but there must be good psych and emotional reasons behind it - decisions made by people who are educated and trained in psychology, psychiatry, victimology, PTSD... Who would believe it could be for any other reason but for the best interest of the siblings?
These are adults, there is nothing legally stopping them from making contact themselves. Jeez, they've been denied contact with the outside world for pretty much their entire lives, so I'm confident that current doctors, therapists and caregivers are treading lightly as far as forbidding them to contact anyone. I assume they could call the hospital themselves and if not speak to someone, leave messages for them? I don't know. I do know, that if the 17 year old could figure out how to make and upload videos to youtube via cell phone
(I CAN'T!!) she could figure out how to do pretty much whatever she sets her mind to.

That includes either teaching her siblings or doing it for them herself.