I have some very cute nephews and a niece. My niece and nephews all have blond hair and are really the sutest children in the universe. I spent several days with my niece and two of my nephews, and had a riot chasing them around, playing in the lake and the sand, and hearing about LIGHTNING McQUEEN! and SHREK! as well as endless "Auntie, why...?" questions.
The annoying thing about the English language is that there's no word for nieces and nephews together. When you have a group of brothers and sisters together, you have siblings. Other languages have words for a group of sibling's children in mixed gender. So our family created one. They are ibbi. My ibbi (consisting of niece and nephew) are crazy fun, tiring, and downright adorable. The only thing that bugs me is that other members of the family use ibbi in the singular. Would you say, "My sibling is being annoying"? Only if they were a hermaphrodite. So, family, unless you are referring to a group which includes ibbi of both genders, please use the gender specific terms niece(s) and nephew(s).