en_tn_condensed/mat/01/11.md

Josiah was an ancestor of Jechoniah

"Josiah was a grandfather of Jechoniah"

at the time of the deportation to Babylon

"when they were forced to move to Babylon" or "when the Babylonians conquered them and made them go live in Babylon."

Babylon

Here this means the country of Babylon, not just the city of Babylon.