Hi Arnold, not really your sisters’ fault as such more of a quirk of nature. Your moms blood group would have been either positive or negative rhesus. Which ever your mom was, your sister would have been opposite. Not a problem with first baby until the birth of your sister. When she was born, some of her blood would have mixed with your moms’ blood and caused your mom to produce an antibody in response.
You would have had the same rhesus factor as your sister, so the antibody in your moms’ blood would have then made you ill. Had you have had the opposite rhesus factor; it would not have been a problem.
In recent years, they now test both the mother and baby’s blood for the rhesus factor and if they are opposite, they give the mother an injection of Anti D. This prevents the formation of antibody’s in the mothers.
It was picked up with my children, so mom had the Anti D and gave birth to two more kids. The condition with the mother having negative rhesus ran in her family. My grandmother would have used the term “blue Baby”
Rhesus babies are quite rare now, they occasional happen when a mother has had a miscarriage first time round, so are not normally treated with Anti D