The only way to be truly bilingual, I believe, is to learn two languages from the getgo. I have a friend who was born and raised in Mexico; his parents were Americans; they spoke English to him, and the servants (over 45 yrs ago) and the outside world spoke Spanish. He is equally comfortable w. both languages and sounds like a native speaker in both. If you adopt, the baby will be receiving a gift if he/she learns English and German as s/he starts to talk. And as a teen, s/he can sass you in both.