It's not that unusual for recording artists to break into the business while they're still young. Years ago, it was the Jacksons, or Steve Winwood, recording at tender ages. More recently, musicians like Adele have broken through before they were allowed to drink alcohol (at least in the United States).
But even so, it seems remarkable that the sister duo called Lily & Madeleine have just released their third album. Keep It Together is out and Lily is only 19 and Madeleine is 21.