Family is a basic unit in society where traditionally, parents raise their children and family bonds survive longer and provide a primary sense of belonging. It has been observed that it become difficult when extended family become complex to find distant relatives using traditional approaches this is due to rural-urban migration and residential mobility, which has been weakened family relationship. Several researchers have developed systems to help relatives in discovering their family relationships using genealogical data, nevertheless, these systems may provide false-positive findings when there is lack of information. In Tanzania the genealogical sites have insufficient individual’s family information for family discovery. The purpose of this paper is to present a developed mobile based application for discovering family relationships with no use of genealogical data and use of rule-based system to identify the type of relationship with a person. Both primary and secondary data collection methods were used to collect data and analyzed using R-studio. The research revealed that rule-based system can easily discover family relationships, and families grow when people interact with the mobile application (MyFam). The system was validated with users, where results emphasized its efficiency as a discovery tool with performance of 40% in user experience, 40% in system functionalities and 55% in system interface. The contribution of this study is to provide a mobile application that can be used in many countries for discovering family members relationships. In addition, due to efficacy of the rule-based system, any relationship can be inferred simply and reliably based on how family relationships are named.