Family communication ; Case study (language acquisition) ; Baby talk; Motherese; Child-directed speech; Ammensprache; Babysprache; Infant-directed speech; Fatherese; Language spoken to children ; Dual language acquisition; Bimodal language acquisition; Spracherwerb (biling.) ; Language acquisition (biling.) ; Bilingual language acquisition ; Differenzierung (Zweisprachiger Spracherwerb) ; Differentiation (bilingual language acquisition) ; Language differentiation (bilingual language acquisition)