Nibling

Her nibling lives in the Netherlands.

His nibling lives in the Netherlands.

Their nibling lives in the Netherlands.

A nibling is the child of a sibling.

The child of a sibling is a nibling.

English has needed a gender-neutral term for niece and nephew for a long time. Why hasn't nibling caught on?

Aunts and uncles are concerned with the education of their niblings and may play a minor role in the ultimate arrangement of a marriage for the nibling.

Very recently I heard an informant respond with cousin to my question about the “child of nibling” position.

In the following line we find Q¹P²; that is, child of a parent of a parent; this is the relation that nuncles (aunts or uncles) bear to niblings (nieces or nephews).

She [Viola Edmundson Garfield] was close to her family, particularly her younger “siblings and niblings.”

Kin selection was strongest for choices between sibling and friend, decreasing across sibling vs. nibling, nibling vs. friend, and nibling vs. cousin, [...]

Most distinctive of the system, therefore, were the two terms for parental siblings and for niblings, which occurred only among the Salish and neighboring Southern Nootkans.

But, it is my niblings who taught me how to love.

Cousins are informally referred to by the same terms used for siblings, but officially one has an aunt/uncle-nibling relationship with one's cousins.