For the most part, English can be spoken and written without references gender, although there are cases where it sounds stiff. “Spouse” can replace “husband” and “wife”; “sibling” can replace “brother” and “sister”.
There are a few problematic pairings, though. Among the most common of these are niece/nephew, aunt/uncle, and sir/ma’am. For niece/nephew, “nibling” is emerging as a popular neologism. In this essay, I’ll explore aunt/uncle.
An emerging term is “auncle”, but I’m not fond of that. In some dialects, that ought to be homophonous with “ankle”; in others, it sounds too much like “uncle”. “Pibling” has also been offered, but with “sibling” and “nibling”, that feels like too much bling on the family tree for my taste.