In Kings II 18, Eliakim is the son of Hilkiah the kohen gadol, in Kings II 23 he is referred to as Jehoiakim son of Josiah. How could he be both?
Based off of Wikipedia (and as per @JoelK's comment) they seem to be 2 different people.
Eliakim son of Hilkiah, succeeded Shebna to become finance minister for King Hezekiah of Judah
Wikipedia says King Hezekiah's reign was between 715 and 686 BC.
2) Jehoiakim son of Josiah (fka as "Eliakim")
was a king of Judah from 609 to 598 BC. He was the second son of King Josiah.
The discrepancy of dates and positions seem to indicate they were 2 different people.