There were a few reasons underlying Denethor’s distaste for Faramir in The Lord of the Rings. J.R.R. Tolkien’s seminal novel was released in three parts between 1954 and 1955, with each of Peter Jackson’s Lord of the Rings movies adapting a part. Faramir and Denethor II were two of the most unfaithful characters in the movies, but they were masterpieces unto themselves. The characters are high fantasy legends, and digging deeper into Tolkien’s lore explains a lot about them and their motivations, which weren’t always totally clear in the cinematic franchise.

https://screenrant.com/why-denethor-hates-faramir-in-lord-of-the-rings-explainer/