Your sister's children sound like they have been vaccine-damaged. They exhibit the same symptoms as thousands of other children and have developed allergies from ingredients that are in vaccines. Breastfeeding them may have prevented even more serious injury to them and she may need to look at her diet and what affects them but it is far superior to their health than formula especially if they are having food reactions. I am very happy for you that it has been a success for you:o)
Please make sure YOU have done the research on vaccinations for YOUR child. The AAP recommended schedule of shots for children is too many, too soon. Here are sites and books that I always recommend for people to start their research and your sister should start with Healing the New Childhood Epidemics: Autism, ADHD, Asthma, and Allergies: The Groundbreaking Program for the 4-A Disorders, by Dr. Kenneth Bock.
The Vaccine Book, by Dr. Robert Sears
What Your Doctor May Not Tell You About Childhood Vaccinations, by Dr. Stephanie Cave
Evidence of Harm, by David Kirby