Is the story of Al-Abbasa and Ja'far al-Barmaki true, and what is the evidence for its truth or falsity?

The story of the marriage of Al-Abbasa and Ja'far al-Barmaki is fabricated and false. Its falsity is supported by the absence of any chain of narration for it in accredited books. Ibn Kathir mentioned one version of it without confirmation, and other scholars denied it. Ibn Khaldun described it as one of the spurious tales that have no basis in truth, emphasizing that the real reason for the downfall of the Barmakis was their tyranny over the state, their withholding of tax revenues, and their control over governmental affairs. Masrur al-Kabir (one of the contemporaries of the events) completely and utterly denied this story.