... dazu weitere englischsprachige WB-Definitionen :

https://www.collinsdictionary.com/submission/...

 nibling

New Word Suggestion

The child of one's sibling; a niece or nephew

Additional Information

It seems to me there should be a word like "sibling" which refers to one's sibling's children, without gender. The word also enables an efficient plural reference to such persons: my niblings. ...

https://www.macmillandictionary.com/dictionar...

 nibling

​noun

DEFINITIONS 1

   1      a niece or nephew

   Let me introduce you to my niblings, Bob and Sue. ...

https://www.onelook.com/?w=nibling&ls=a

one look hat nur Treffer im “Urban Dictionary” und in der “Wiktionary” gefunden. Wenn in letzterer nicht stünde, dass ein amerikanischer Linguist bereits 1951 den Begriff kreiert hat, hätte ich angenommen, das sei eine Neuschöpfung aus dem letzten Jahrzehnt und man müsse noch ein wenig abwarten, ob das ein Modewort ist oder ob es gekommen ist, um zu bleiben. Eigentlich ein sehr praktisches Wort. Auf Deutsch müsste man dazu entsprechend wohl Neschwister sagen ;o))

Nefichten?

Ich finde niblings super, wir haben aber auch ca. 10 davon, bis auf eine alles Brit*innen.

Nechten wäre noch eine Möglichkeit, oder Niffen. Ich bräuchte eher eine deutsche geschlechtsneutrale Bezeichnung entsprechend dem englischen cousin, davon habe ich nämlich 13. Die jeweiligen Ehepartner noch nicht mitgerechnet.

Geschwisterkind

https://www.duden.de/rechtschreibung/Geschwis...

https://www.theguardian.com/money/2005/apr/17...

Paul has so many 'niblings' he doesn't know what to do

I want to be equitable to all my 'niblings' and assist mainly with their higher education and early adult life costs. However, one - now nine years old - is severely autistic, and will require lifelong support.

Paul's to-do list

1. Decide whether you want to stay in control or put your savings into your 'niblings' names.

https://www.theguardian.com/global/2018/dec/1...

This is how it goes for my nephews and nieces (henceforth, niblings) each Christmas morn, when my packages finally reach their grubby little paws. 

http://newsimg.bbc.co.uk/cbbcnews/hi/uk/newsi... (28 April 2004)

A group of Somerset schoolchildren have launched a bid to get the word nibling into the Oxford English Dictionary. Nibling is a little-known word which means "niece or nephew". It'll be part of everyday speech if the Paulton Junior School kids get their way.

https://www.merriam-webster.com/words-at-play...

As the previous millennium has receded, however, nibling has started to show signs of life. We received another letter concerning the word in 2005, this time from a correspondent in Ft. Lauderdale. And evidence of the word in use began to appear in print as well, though more often on the other side of the proverbial pond:

Schoolchildren in Paulton are campaigning to get a new word into the English dictionary. They are urging friends and family to use the word 'niblings' instead of the phrase nieces and nephews in an attempt to earn it a place in the Oxford English Dictionary.

— Chris Allen, The Bristol (UK) Post, 30 Apr. 2004

From the BBC article in #8: "A group of Somerset schoolchildren have launched a bid to get the word nibling into the Oxford English Dictionary. It'll be part of everyday speech if the Paulton Junior School kids get their way."

@ #9

...provided the children of Paulton Junior School take over :)