panzi -paz- gismu

x1 is a [biological] offspring/child/kid/hybrid of parent(s) x2; (adjective:) x1 is filial.

See also grute, verba, bersa, tixnu, se rorci, patfu.

In notes:

bersa
x1 is a son of mother/father/parents x2 [not necessarily biological].
grute
x1 is a fruit [body-part] of species x2.
patfu
x1 is a father of x2; x1 begets/sires/acts paternal towards x2; [not necessarily biological].
rorci
x1 engenders/procreates/begets x2 with coparent x3.
tixnu
x1 is a daughter of mother/father/parents x2; [not necessarily biological].
verba
x1 is a child/kid/juvenile [a young person] of age x2, immature by standard x3.
lanpanzi
p1 is a lamb of species/breed l2
pavmompazy'utka
x1 is path-connected to x2 via the (non-gendered/absolute) first-born progeny/primogeniture relation; x1 is the first-born offspring of the first-born offspring of ... the first-born offspring of x2, connected by a graph-path passing through intermediate relations/steps (successive first-born offspring) x3 (ce'o; ordered list), "first" being according to ordering rule x4 (default, as used in this definition: chronological order of birth; restrictions on legitimacy etc. may also be included here).
selrorci
x2=r1 engenders/procreates/begets x1=r2 with coparent x3=r3.
paznu
x1 is a non-binary offspring/child of parent(s) x2 [not necessarily biological]; x1 is filial (but not a son or daughter).