The principals of the Bucks County firm formerly known as Mellon Webster & Shelly are currently embroiled in litigation with each other over the firm’s succession plan in the wake of its leader’s diagnosis with a serious illness.

Former shareholder Carol A. Shelly filed suit in the Bucks County Court of Common Pleas on April 23 against Thomas Mellon Jr., the firm’s president, chief executive officer and chief financial officer, and his wife, Sara Webster, who is also a shareholder with the firm.