<p>This paper introduces a novel prioritisation method, the Thematic Hierarchy Process, designed to work with software release cycles in a matrix product development organisation with software product lines and multiple business lines. Three challenges are identified for prioritisation of requirements for software product lines with multiple business lines: scale, complexity and stakeholder discordance. The paper reviews current prioritisation methods and assesses their application to software product lines with multiple business lines with respect to these three challenges, and concludes that none of the existing methods can satisfactorily address all of them. In this paper we define the Thematic Hierarchy Process method, and provide a framework that can be applied by software product managers and researchers to their own software releases and requirements data. The Thematic Hierarchy Process was assessed using requirements data from Company A demonstrating strong alignment with real software release cycles, as shown by the high similarity scores of 0.87 and 0.91 in predicting release contents. Interviews carried out with domain experts to evaluate the Thematic Hierarchy Process to supplement the assessments also showed positive results. We conclude that the Thematic Hierarchy Process can satisfy the prioritisation challenges of scale, complexity and stakeholder discordance with software product lines with multiple business lines.</p>