As a linguistics nerd, I’d like to formally suggest “Nespring” as a nonbinary equivalent to niece/nephew and “Avaun” as a nonbinary equivalent to aunt/uncle
Nespring: literally meaning “the offspring of my sibling” from the old English roots “offspring” which is just ‘of spring’ and the Latin root “nepos” that both niece and nephew are derived from
Avaun: derived from the roots of both “aunt” and “uncle,” the anglo-French “aunte” and the Latin “avunculus”
a grown man: haha I’m such a baby I don’t know how to take care of myself because women, including my mother, have wasted decades of their precious lives and time and energy doing everything for me and now I’m a lazy pathetic unfeeling shithead. it’s so sweet that I don’t know how to chop an onion or use fabric conditioner haha awh I need a girlfriend to look after me