Another 44+ Millie Bobby Brown Age 12. Her birthday, what she did before fame, her family life, fun trivia facts, popularity rankings, and more. Learn about millie bobby brown: Millie bobby brown was born on 19 february 2004 making her 16 years of age in 2020 and she will turn 17 in the year 2021. At the age of twelve, she gained notability for her role as eleven in the first season of netflix science fiction series stranger.