Gender-neutral kin terms in English

[Chuma]

I'm working on a text which deals with various types of relatives (in more of a mathematical sense, but anyway), and so I needed a gender-neutral term for "aunt" / "uncle". I came across a few linguistic abominations like "parsib", "pibling", or "auncle", but also the interesting term "ommer". I can't find any etymology for it; the only thing that mentions it is a Wiktionary entry for a presumably unrelated word in Danish.

So, do any of you know the origin of this word? Or do you have other suggestions for terms?

In my natlang Swedish, as in many others, these terms are even more distinct; in relation to my nephews, I would simply be "mother-brother". So no inspiration there. But I'm fairly sure there are other languages that don't distinguish gender here – maybe some suitable loan word?

[Kuchigakatai]

If it's only text and you don't care about pronunciation, there is Spanish tí@.

Some Spanish-speaking gender-critical people nowadays also use tíe [ˈti.e].

Mandarin uses 叔伯姑姨 shūbógūyí as a generic term for 'one's uncles and aunts'. Morphologically, this breaks down as shū- 'father's younger brother', -bó- 'father's older brother', -gū- 'father's sister', -yí 'mother's sister'. (The "missing" distinct morphemes are 舅 jiù 'mother's brother' and 婶 shěn 'father's younger brother's wife'. "Missing" relationships here are made with compounds of these morphemes plus 妈 mā 'mother', 母 mǔ 'female' or 夫 fū 'husband, man'.) Compare this with the Mandarin word for 'one's siblings', 兄弟姐妹 xiōngdìjiěmèi, literally "older.brother-younger.brother-older.sister-younger.sister'.

[Darren]

Regarding the etymology of ommer, I found a post on an asexuality forum here where someone suggests it comes from English eam, a dialectal word for "uncle," or related Germanic words like German Ohm, Dutch oom, ultimately from PG *awahaimaz and PIE *h₂éwh₂os. They also suggest an etymology in modrige which looks more questionable. Ther -er looks more like a diminuitive/endearment thing like some English nicknames (e.g. Rugger for Rugby).

For synonymous terms, I can also find ackle; there are probably a few more neologisms. I'd agree that ommer sounds the best and is the only one which looks like a native term.