bruna -bun-bu'a- gismu

x1 is brother of/fraternal to x2 by bond/tie/standard/parent(s) x3; [not necess. biological].

See also mensi, tunba, tamne, famti, bersa.

In notes:

bersa
x1 is a son of mother/father/parents x2 [not necessarily biological].
famti
x1 is an aunt/uncle of x2 by bond/tie x3; x1 is an associated member of x2's parent's generation.
mensi
x1 is a sister of/sororal to x2 by bond/tie/standard/parent(s) x3; [not necessarily biological].
tamne
x1 is cousin to x2 by bond/tie x3; [non-immediate family member, default same generation].
tunba
x1 is a sibling of x2 by bond/tie/standard/parent(s) x3.
selbu'a
x2=b1 is brother of/fraternal to x1=b2 by bond/tie/standard/parent x3=b3.
selfamti
x1 is an niece/nephew of x2 by bond/tie x3.
terbu'a
x3=b1 is brother of/fraternal to x2=b2 by bond/tie/standard/parent x1=b3.
paznu
x1 is a non-binary offspring/child of parent(s) x2 [not necessarily biological]; x1 is filial (but not a son or daughter).
pentu
x1 is a non-binary sibling of/to x2 by bond/tie/standard/parent(s) x3; [not necessarily biological].
bun
Brother