I find it handy when talking about my sons and daughters I can just say my children. It’s nice to say nieces instead of sibling’s daughters. I wonder if there is a similar term for nieces and nephews together? I imagine I could say sibling’s kids but I was hoping for a single word.
There seems to be no “official” word for “nieces and nephews”.
You will find “nibling”, by analogy with sibling. (But it is mentioned only in the “New Words & Slang” section of Merriam-Webster, or in sites like urbandictionary.com)
In this Yahoo answers thread, KISS = Keep It Simple, Stupid’s answer also mentions:
that there is no encompassing word for aunt/uncle either
that there is no male/female form of cousin.
The article “There isn’t a word for it” (by Neville Goodman, British Journal of General Practice, 2005) also confirms that there is no word for nephews and nieces, and makes the following (humorous) suggestions:
The word sibling comes from Old English, and just means related by blood. I suggest taking the parental ‘p’ to replace the ‘s’, so aunts and uncles are ‘piblings’. Following the pattern, nephews and nieces become ‘niblings’, a nice word that describes what they do to their piblings’ bank balances at Christmas and birthdays.