WTF Fun Fact – Nibling

 The gender neutral term for a niece or nephew is a nibling, just like the gender neutral term for a brother or sister is a sibling. – WTF Fun Facts

Source: https://www.merriam-webster.com/words-at-play/words-were-watching-nibling#:~:text=Nibling%20is%20a%20gender%2Dneutral,being%20revived%20in%20recent%20years.