Different children have different reactions. My younger brother doesn’t remember much about our older brother, Michael. Michael is autistic, low functioning and nonverbal. Mom and Dad both said that they tried shielding us kids from the brunt of Mike’s influence. I suppose it worked, for one of us. Maybe there was a little magic thrown in as well.
I consider myself more of the Sputnik generation than my younger brother. This is probably one of the reasons I remember and try to analyze everything.
Prior to the 1970s, the Freudians held sway in the mental health arena, and god help the patient if he or she didn’t fit into the mold of how they defined mental illness. Take a look at Madness on the Couch  for more information about this. The subtitle of this book is Blaming the Victim in the Heyday of Psychoanalysis.
This should give you a good idea of my parents’ environment in 1949 as they sought answers and help to understand their difficult, retarded son who did not learn to talk. My older brother’s other symptoms had only been recently described at that time (1943) in the psychiatric literature.  Today, those symptoms describe autism. In the 1950s and 60s, parents were accused of causing their children’s autism. The famous ‘refrigerator mother‘ theory stated that a cold family environment was the cause of autism.
Those were different days. Today there are scientific studies being done on all aspects of the complex problem of autism spectrum disorders (ASD), and siblings of those affected are at least acknowledged. Even today however, there are still times when some physicians who cannot figure out why one of their charges is sick, will tell him or her to see a psychiatrist. Blaming the victim is still with us, and we must be wary of it.
Different children will still grapple with a family dynamic that includes a handicapped sibling in different ways. They must still handle emotions of anger, frustration and guilt mixed in with futility and sadness. I venture to say that one sibling might experience blocked memories and one might try unceasingly to understand the unknowable.
Hopefully each will come to some kind of equilibrium