[ᴱ]^ᴺ√RE(N)D root. “kinsman, *cousin”
ᴱ√REÐE root. “kinsman”
The form reðe was a root added under ᴱ√RESE [REÞE] “aid, support” in the Qenya Lexicon of the 1910s, with derivatives of ᴱ√RESE having to do with “kinship” reassigned to reðe, such as ᴱQ. renda “related, of the same kin or clan” and ᴱQ. resse “kinswoman, cousin” (QL/79). In the contemporaneous Gnomish Lexicon Tolkien had a similar set of words likewise derived from distinct reth- vs. redh-, with the latter most likely being the basis for words like G. redhin “related” and G. ress “cousin (f.), relative” (GL/65). The root was given as RESE- “kinsman” in the Poetic and Mythological Words of Eldarissa (PME/79), but the addition of reðe may be later than that document.
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is worth positing a Neo-Root ᴺ√RE(N)D to preserve these early kinship and cousin words, for which we have no later alternatives. It might be considered a variant of later root √RED “scatter, sow” (Ety/RED; PE19/91) and thus applied only to more distant kin.
References ✧ GL/65; PME/79; QL/79