Millie Bobby Brown and husband Jake Bongiovi adopted a baby girl. (JB Lacroix/FilmMagic)Millie Bobby Brown is a mom. The Stranger Things actress, 21, and her husband, Jake Bongiovi, 23, announced via an Instagram post that they adopted a baby girl."This summer, we welcomed our sweet baby girl through adoption. We are beyond excited to embark on this beautiful next chapter of parenthood in both peace and privacy," Brown wrote on Instagram. She concluded the post with, "And then there were 3."Brown, who will star in the final season of Stranger Things when it drops on Netflix beginning Nov.