A word in the Gnomish Lexicon of the 1910s glossed “consanguinity”, an abstract noun formation from †hest “brother or sister” with variants hestri and hethri (GL/49). It also had variants G. gochestri and gochethri with the prefix G. go- “together” (GL/40).
Gnomish
hest
noun. brother or sister, *sibling; †consanguinity
hestri
noun. consanguinity
gochestri
noun. consanguinity
hethir
noun. sister
hethos
noun. brother
gochethri
noun. consanguinity
hethri
noun. consanguinity
hothron
noun. captain
A word appearing as G. hest in the Gnomish Lexicon of the 1910s for “brother or sister” [sibling], but “properly consanguinity, the relationship of brother and sister, or brother and brother, etc.” (GL/48); this original meaning seems to be archaic, transferred to G. hestri or G. gochestri. This word is derived from the early root ᴱ√heth (GL/48).
Neo-Sindarin: For purposes of Neo-Sindarin, I would retain the word ᴺS. hest as a derivative of the Neo-Root ᴺ√KHETH to serve as a gender-neutral term for “sibling”.