I have a friend who has twins the same age as mine. When they were little, they had developed this, sort of, secret language which so many people refer to as "twin talk." One would say, "ba ba ba ba," and the other would say, "boo boo boop," and they totally understood each other. It was really cute. What happened was found out that her kids actually had a speech delay. What I think people don't understand is that, because there is sort of this mystic around twins and they have a secret language that only they understand, that parents don't step in and realize, maybe the children aren't having enough adult interaction. People tend to just let twins play together. They always want to be together. The more you talk to your twins in adult language, the more they will learn language and not just baby talk or twin talk.