Board Thread:Episode Discussions/@comment-25086462-20170412225621/@comment-27797856-20170608090815

QuakingStar wrote: They are 6, Lux. Where the hell is this coming from?

The war was said to had happened more than ten years ago. (And "Boruto: Naruto the Movie" was confirmed to be 15 years after Shippūden).

Plus we have official ages for, at the very least, Sarada in the Scarlet Spring short, where she was confirmed to be 11.