Co-teaching is described as the pairing of a general education teacher and a special education teacher in the general education classroom for the shared instruction of students with and without disabilities. Many teachers struggle to form unified partnerships, especially in mathematics classrooms. The MathMATES project was developed to address a need for joint special education and mathematics professional development aimed to support teachers in merging their individual strengths and expertise through shared content development and relationship-building exercises. Over the course of the year-long academy, teachers developed strong knowledge-sharing partnerships that resembled co-mentoring partnerships. We compare their progression with research on co-mentoring to suggest a framework for developing more unified mathematics co-teaching teams.