Have you heard of a book called "Toilet Training in Less Than a Day" by Nathan Azrin? He developed his methods to toilet train institutionalized individuals who were profoundly mentally retarded, and was successful. After learning how much trouble parents were having training their children, he adapted his methods and wrote this book. It's was written over 20 years ago. I successfully used his program to toilet train first my son, then my daughter, in one day. (They are now young adults.) They're not twins, and I did the training before they were 2 1/2. The book includes a "readiness test" to assess if your child is developmentally ready. I was a psychology major in college, so I was comfortable with the methods he used. You do need to have a day to devote to each child, so your husband or someone else would need to take the other two children for 6-10 hours. I decided to try and toilet train my son before we took him on a Mexican vacation. At that time, Mexican disposable diapers were terrible, and we did not want to bring along a 3 week supply of Pampers. He still needed a diaper at night, and sometimes during naps, but we did not have to bring along a suitcase full of diapers. Everywhere we went in Mexico, our son announced he had to go potty. My husband got a tour of all the public restrooms. What a treat!