How do I know I have Third Culture Kids? Because they keep switching between languages without any trouble, my son knows more about geography then the average adult and he even told me that being in the same school for six years must be sooooooooo boring!
If you want to read more about this subject I can recommend "Third Culture Kids. Growing Up Among Worlds" by David C. Pollock and Ruth E. van Reken. And see the website: http://www.tckworld.com/