I have all kinds of relatives, and many of them are cousins, for sure. However, some others of them are great aunts and uncles and all of their kids and their kids' kids are my cousins. My first cousin's kids are my cousins (but call me Aunty). I just introduce them as my neice and nephew, cuz it is easier that way. My sister's kids are my niece and nephew for real. When they have kids, those babies will be my great nieces and/or nephews, since I'll be there great-aunt.