It is true that kids might be confused a little bit at the beginning, when there are two different labels for things, or they need to use different languages to talk to different people. It can be normal for children learning more than one language to experience what’s known as “interference” — when the grammar and structure of one language influences the grammar of the other language they are learning, which leads to grammatical errors. This is not a language disorder, but a normal part of learning two languages.