Balance control probably has the greatest impact on independence in activities of daily living (ADL), because it is a fundamental motor skill and prerequisite to the maintenance of a myriad of postures and mobile activities. We propose a new rehabilitation therapy to administer standing and mobile balance control training, enabled by a Mobile Robotic Assistive Balance Trainer (MRABT). The targeted group for this initial work is post stroke patients, although it can be extended to subjects with other neurological insults in the future. The proposed system consists of a mobile base and a parallel robotic arm which provides support to the patient at the hip. The compliant robotic arm with intelligent control algorithm will only provide support and assistance to the patient when the center of mass of the body deviates beyond the predefined safety boundary, mimicking the helping hands of a parent when a toddler learns to walk. In this paper, we present our initial work in the design and kinematic analysis of the system.