The Same Noble Line by Melanie Rachel

He can have Pemberley or his honour—but not both.

Haunted by his own suspicions and revelations in his grandfather’s journals, Fitzwilliam Darcy uncovers a devastating possibility: the indolent Mr. Thomas Bennet may be Pemberley’s rightful heir. The estate that has defined Darcy’s family for generations could slip from his grasp—and into the hands of a man whose own estate suffers from neglect.
Already bewitched by Miss Elizabeth Bennet, Darcy returns to Hertfordshire to investigate, accompanied by his cousin Colonel Fitzwilliam and sister Georgiana. But pursuing Elizabeth now seems impossible, for how can he court her while concealing that her father might be entitled to everything Darcy possesses?
As each visit to Longbourn deepens his attachment, Darcy watches his options narrow. To reveal his secret would make him appear a fortune hunter in her eyes, while his continued silence might make him complicit in denying her family its due.

Meanwhile, Pemberley’s fate—and his own future—hang in the balance.