Gnomish
ren(d)
noun. cousin (m.), relative
goredhweg
noun. cousin (m.)
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
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.