cherub

foundling, nursling, suckling

preemie (also premie)

bantling, kid, kiddie (also kiddy), kiddo, moppet, toddler, tot, tyke (also tike)

boy, nipper, tad

juvenile, minor, youngling, youngster, youth

brat, imp, squirt, urchin, whippersnapper

girl, hoyden, tomboy