Gnomish
ren(d)
noun. cousin (m.), relative
goredhweg
noun. cousin (m.)
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
G. ren(d) appeared in the Gnomish Lexicon of the 1910s as a word for a male cousin or relative based on the early root ᴱ√redh- (GL/65). It had poetic equivalents G. redhweg and redhos; and the first of these also appeared in the more elaborate form G. goredhweg (GL/41). Two more variants, G. hethren and G. {gedrend >>} gedren, referred to first and second male cousins respectively, with the prefixes G. heth (for close relation) and G. ged (a more distant relation) respectively (GL/38; GL/48).
Neo-Sindarin: I would retain ᴺS. rend as a Neo-Sindarin word for “male cousin or relative” as a derivative of the Neo-Root ᴺ√RE(N)D, but would abandon all the more elaborate variants.