A root for “brother” that Tolkien introduced in notes on finger-names from the late 1960s as a companion to √NETH “sister” (VT47/14, 26, 34). It conflicts with, and possibly replaces, earlier uses for √KHAN such as √KHAN “back” in notes from around 1959 serving as the basis for the prefix Q. han- in hanquenta “answer” (PE17/166). The root ᴹ√KHAN also appeared in The Etymologies of the 1930s glossed “understand, comprehend”, with various derivatives in both Quenya and Noldorin of similar meaning (Ety/KHAN).
It is unlikely that all these uses of √KHAN coexisted, but I think at a minimum both √KHAN “brother” and ᴹ√KHAN “understand, comprehend” should be retained for the purposes of Neo-Eldarin, as the latter has no good replacements in Tolkien’s later writing. As for hanquenta “answer”, it might be reinterpreted as “a saying providing understanding”, and so be derived from ᴹ√KHAN “understand”.
A root appearing in 1964 notes on Dalath Dirnen (DD), with the gloss “secrete, hide” and serving as the basis for S. torn “hidden, secret” and S. torech “secret hole, lair” as in S. Torech Ungol “Shelob’s Lair” (PE17/188). Since this root appears nowhere else with this gloss and S. Torech Ungol has other translations elsewhere, such as “Tunnel of the Spider” (RC/490), I would be cautious about using this root.