In Ahab's days, who rebuilt Jericho at the cost of his firstborn and youngest sons?

Answer: Hiel the Bethelite

Hiel laid Jericho's foundation at the cost of Abiram and set up its gates at the cost of Segub, as the LORD had spoken through Joshua.

“In Ahab’s days, Hiel the Bethelite rebuilt Jericho. At the cost of Abiram his firstborn he laid its foundation, and at the cost of Segub his youngest he set up its gates, according to the word that the LORD had spoken through Joshua son of Nun.”— 1 Kings 16:34 (BSB)