Part I of the family vocab series is here.
“Child” is بَچّه (bachchah, plural بَچّهها bachchahhā or بَچّگان bachchagān) or فَرزَند (farzand, plural فَرزَندان farzandān). “Baby” is کودَک (kūdak, plural کودَکان kūdakān) or نَوزاد (nawzād, plural نَوزادان nawzādān).
“Son” is پِسَر (pisar, “peh-sar,” plural پِسَران pisarān or پِسَرها pisarhā), which also means “boy.”
“Daughter” is دُختَر (dukhtar, “dokh-tar,” plural دُختَران dukhtarān or دُختَرها dukhtarhā), which also means “girl.”
Persian Word a Day 