(n.) The daughter of one's son or daughter.

adolescent angel artifact babe baby bairn boy brainchild brat brood bud cherub chick chickabiddy child of nature chit coinage composition concoction creation creature crowning achievement darling daughter descendant descendants dickens distillation dove dupe effect end product essence extract foetus foster child fruit girl grandchild granddaughter grandson handiwork heiress hick infant ingenue innocent invention issue juvenile kid kitten lad laddie lamb lambkin lass lassie little bugger little fellow little guy little innocent little one little tad little tot lout manufacture masterpiece masterwork mere child minor mintage mite moppet neonate new mintage newborn newborn babe nipper noble savage oaf offspring opera opus opuscule origination outcome outgrowth peewee posterity product production progeniture progeny puss result rube runabout scion seed shaver simple soul small fry son son and heir sonny stepchild stepdaughter stepson stripling tad teenager teener teenybopper toddler tot unsophisticate wee tot work yokel young hopeful young man youngling youngster youth